Dissertations / Theses on the topic 'Molecules and Processes'
To see the other types of publications on this topic, follow the link: Molecules and Processes.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Molecules and Processes.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Vichetti, Rafael Mário [UNESP]. "Síntese dos isótopos do monóxido de carbono no meio interestelar." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/91889.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:25:31Z (GMT). No. of bitstreams: 0
Previous issue date: 2009-12-21Bitstream added on 2014-06-13T19:53:20Z : No. of bitstreams: 1
vichietti_rm_me_rcla.pdf: 842604 bytes, checksum: 731ca276a75c1b92840e57bd7497b5e1 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
De acordo com os resultados observacionais de condensações de nuvens moleculares escuras, grandes variações na razão 13CO/C18O são observadas quando se comparam os resultados obtidos nas condensações situadas dentro da mesma nuvem, bem como de nuvem para nuvem. O valor médio dessa razão na condensação principal de Ophiuchus é inferior a 5. Por outro lado, o valor encontrado nas condensações que estão situadas ao norte de Oph é maior que 10. Grandes diferenças também são encontradas quando se comparam os resultados observacionais de diferentes nuvens escuras, tais como Ophiuchus e Taurus, onde são observados também um decréscimo da razão C18O/C17O com o aumento da densidade. Os processos químicos e físicos que governam essas variações ainda não estão claros. Nesse sentido, o objetivo da presente proposta é analisar a influência do colapso gravitacional de condensações de nuvens moleculares escuras na síntese das moléculas CO, C17O, C18O, 13CO, 13C17O e 13C18O. Tal análise é feita com base em comparações entre modelos que consideram diferentes condições entre si, tais como, tamanho da cadeia química, velocidade de colapso, densidade inicial e processos de congelamento de espécies químicas na superfície de grãos de poeira. Os resultados obtidos mostram que o tamanho da cadeia química tem influência nas razões 13CO/C18O e C18O/C17O, mas não tanto quanto a densidade inicial e a velocidade do colapso. Além disso, o congelamento das espécies químicas nos grãos é mais significativo nos estágios mais avançados da evolução da condensação. Os modelos de condensações escuras que sofrem colapso gravitacional lento e em queda livre reproduzem satisfatoriamente as razões 13CO/C18O e C18O/C17O observadas, o que permite concluir que o colapso gravitacional pode ter um importante efeito nas referidas razões.
According to the observational results of dark molecular clouds condensations, large variations in the ratio 13CO/C18O are observed when comparing the results obtained in the condensations located within the same cloud and cloud to cloud. The average value of this ratio in the main condensation of Ophiuchus is below 5. On the other hand, the value found in the condensations that are located north of Oph is larger than 10. Large differences are also found when comparing the observational results of different dark clouds such as Ophiuchus and Taurus, in which are also found a decrease of the C18O/C17O ratio with increasing density. The chemical and physical processes that govern these variations are still unclear. In this sense, the objective of this proposal is to analyze the influence of the gravitational collapse of centrally condensed clumps of dense molecular gas in the synthesis of the CO, C17O, C18O, 13CO, 13C17O and 13C18O molecules. This analysis is based on comparisons among models that consider different condition, such as, chemical chain, initial density, speed of collapse and freezing processes of the chemical species on the surface of dust grains. The results show that the size of the chemical chain has influence on the 13CO/C18O and C18O/C17O ratios, but they are not as important as the initial density and the speed of the collapse. Furthermore, the freezing of chemical species on the grains occurs at later times of the collapse. The models of a gravitational free-fall collapsing core and of slowly contracting core with higher initial density are consistent with observations. These results indicate that the gravitational collapse of molecular cores can have an important effect in the 13CO/C18O and C18O/C17O ratios.
2
Bryan, William Alexander. "Ultrafast processes in small molecules." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248347.
Full text
3
Chen, Tao. "Ions colliding with molecules and molecular clusters : fragmentation and growth processes." Doctoral thesis, Stockholms universitet, Fysikum, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-117114.
Full textAbstract:
In this work we will discuss fragmentation and molecular growth processes in collisions of Polycyclic Aromatic Hydrocarbon (PAH) molecules, fullerenes, or their clusters with atoms or atomic ions. Simple collision models as well as molecular structure calculations are used to aid the interpretations of the present and other experimental results. Fragmentation features at center-of-mass collision energies around 10 keV are dominated by interactions between the fast ion/atom and the electron cloud in the molecules/clusters (electronic stopping processes). This electronic excitation energy is rapidly distributed on the vibrational degrees of freedom of the molecule or of the molecules in a cluster and may result in fragmentation. Here, the fragmentation is statistical and favors the lowest-energy dissociation channels which are losses of intact molecules from clusters, H- and C2H2-losses from isolated PAHs, and C2-loss from fullerene monomers. We will also discuss the possibility of formation of molecular H2 direct from native PAHs which reach high enough energies when interacting with ions, electrons, or photons. For the experiments at lower center of mass collision energies (~100 eV) a single atom may be knocked out in close atom-atom interaction. Such non-statistical fragmentation are due to nuclear stopping processes and gives highly reactive fragments which may form covalent bonds with other molecules in a cluster on very short time scales (picoseconds). This process may be important when considering the formation of new species. For collision between 12 keV Ar2+ and clusters of pyrene (C16H10) molecules, new molecules, e.g. C17H10+, C30H18+, C31H19+, etc are detected. We also observe molecular fusion processes for He and Ar ions colliding with clusters of C60 molecules. These and related molecular fusion processes may play a key role for understanding molecular growth processes under certain astrophysical conditions.
4
Vidonne, Annick. "Integrating replication processes with mechanically interlocked molecules." Thesis, St Andrews, 2009. http://hdl.handle.net/10023/913.
Full text
5
Toliautas, Stepas. "Electronic excitation processes of photoactive organic molecules." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20140929_100526-37294.
Full textAbstract:
Evolution of the electronic excitation is a general process that can be used to explain many natural and artificial phenomena, such as photosynthesis in plants and bacteria, biological mechanism of vision, and operating principles of optomechanical and optoelectronic devices. This process is theoretically modeled by solving the time-dependent Schroedinger equation. However, such treatment is too computationally expensive to be used for practical molecular systems. Therefore, either models of the structure of the systems or the solving procedure itself must be simplified to get the desired results. The main goal of the research presented in this dissertation was to study processes caused by the electronic excitation in photoactive molecules using computational methods of electronic structure (i. e. solving the simpler time-independent Schroedinger equation) and to construct the potential energy surface models describing the energy relaxation in the investigated molecules. It is shown that the results of different investigations performed using the same procedure provide explanations of different phenomena in various compounds, such as: proton transfer in polar solvent, performed by a functional group of the bacteriorhodopsin protein; optomechanical cycle of the indolo-benzoxazine compound; efficient phosphorescence of the silicon-based organic polymer; and optical properties of organometallic emitter compound with additional charge-carrier groups.Elektroninio sužadinimo evoliucija šviesai jautriose molekulėse yra reiškinys, kuriuo remiantis įmanoma nagrinėti daugelį natūralių ir dirbtinių procesų: augalų ir bakterijų fotosintezę, regos mechanizmą, optomechaninių bei optoelektroninių prietaisų (pavyzdžiui, organinių šviestukų) veikimą. Teoriškai šis reiškinys modeliuojamas sprendžiant laikinę Šriodingerio lygtį. Deja, toks sprendimas realiems, praktiškai panaudojamiems junginiams šiandien yra per sudėtingas uždavinys, todėl jį tenka keisti supaprastinant nagrinėjamų junginių modelius arba sprendimo metodiką. Šioje disertacijoje aprašomų tyrimų tikslas buvo elektroninės struktūros skaičiavimų metodais (t. y. sprendžiant paprastesnę nuostoviąją Šriodingerio lygtį) ištirti elektroninio sužadinimo sukeltus procesus fotoaktyviose molekulėse ir sudaryti sužadinimo relaksaciją apibūdinančius potencinės energijos paviršių modelius. Parodoma, jog ta pačia metodika atliekamų tyrimų rezultatai paaiškina įvairiuose junginiuose vykstančius reiškinius: bakteriorodopsino baltymo funkcinės grupės vykdomą protono pernašą poliniame tirpiklyje, indolo-benzoksazino junginio optomechaninį ciklą, našią fosforescenciją organiniame silicio polimere bei šviestukams naudojamo metaloorganinio komplekso su prijungtomis krūvininkų pernašos grupėmis ypatybes.
6
Howle, Christopher Roy. "Decay processes of photoexcited molecules in the VUV : comparison with ion/molecule reactions." Thesis, University of Birmingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421712.
Full text
7
Suárez, Rojas Noslen. "Strong-field processes in atoms and polyatomic molecules." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/461458.
Full textAbstract:
In this thesis, we develop a general theory to describe the dynamics of electrons that are ionized when an atom or molecule is exposed to a strong low frequency laser field. Our approach extends and improves the well-established theoretical strong-field approximation (SFA). Additionally, our modified strong field approximation (MSFA) can be extended in a natural way from atomic systems to a more complex molecules and multielectron systems. Our scheme involves two innovative aspects: (i) First, the bound-continuum and rescattering matrix elements can be analytically computed for both atomic and multicenter
molecular systems, using a nonlocal short range (SR), but separable, potential. When compared with the standard models, these analytical derivations make possible to directly examine how the ATI and HHG spectra depend on the driven media and laser-pulse features. Furthermore, our model allows us to disentangle the different processes contributing to the total spectra, amongst other capabilities, and it allows us to adjust both the internuclear separation and atomic or molecular potential in a direct and simple way. Furthermore, we can turn on and off contributions having distinct physical origins or corresponding to different mechanisms that correspond to (1) direct tunneling ionization; (2) electron escattering/recombining
on the center of origin; and, finally, (3) electron rescattering/recombining on a different center. (ii) Second, the multicenter matrix elements in our theory are free from nonphysical coordinate-systemdependent terms; this is accomplished by adapting the coordinate system to the center from which the corresponding time-dependent wave function originates. Having established the basic formalism, we then study the HHG and ATI processes for a variety of atomic and molecular systems. We compare the SFA results with the full numerical solutions of the timedependent Schrödinger equation (TDSE), when available, within the few-cycle pulse regime. We show how our MSFA can be used to look inside the underlying physics of those phenomena. With our tool it is possible to investigate the interference features, ubiquitously present in every strong-field phenomenon involving a multicenter target, or to describe laser-induced electron diffraction (LIED) measurements
retrieving molecular structural information from the photoelectron spectra. Our approach paves the way to study the HHG and ATI processes in much more complex molecular targets. Additionally, it potentially can be extended to study these kind of recombination and rescattering scenarios in solid targets.En esta tesis, desarrollamos una teoría general para describir la dinámica de ionización de electrones cuando un átomo o molécula está expuesto a un campo externo fuerte y de longitud de onda larga. Nuestra teoría: la aproximación de campo fuerte modificada (MSFA), es capaz de describir la interacción de un pulso de luz, no sólo con átomos sino también con moléculas y sólidos. La MSFA está construida como una extensión natural y consecuente del modelo atómico, describiendo desde los sistemas más simples hasta las moléculas más complejas, incluyendo sistemas de muchos electrones. Nuestro enfoque abarca dos aspectos innovadores: (i) En primer lugar, los elementos de matriz que describen la dispersión e interacciones de electrones en el continuo se calculan analíticamente, tanto para sistemas atómicos como moleculares. Esto se logra utilizando un tipo de potencial de corto alcance (SR), no local y separable. En comparación con los modelos estándares, estas derivaciones analíticas permiten examinar directamente cómo los espectros ATI y HHG dependen de las características del pulso láser. Nuestra derivación analítica permite diferenciar los diferentes procesos que contribuyen al espectro total, además de que nos permite fijar la distancia internuclear y el potencial atómico o molecular de una manera directa y sencilla. También es posible activar y desactivar las contribuciones que tienen diferentes orígenes físicos o que corresponden a diferentes mecanismos como, (1) ionización directa por túnel; (2) dispersión/recombinación de electrones en el átomo de ionización; y, por último, (3) dispersión/recombinación de electrones en un átomo distinto al de ionización. (ii) En segundo lugar, en nuestra teoría los elementos matriciales de los sistemas multi-atómicos se encuentran libres de calibraciones no físicas y son independientes del sistema de coordenadas. Esto se consigue adaptando el sistema de coordenadas al átomo del que se origina la correspondiente función de onda dependiente del tiempo. Una vez establecido el formalismo básico del MSFA, estudiamos los procesos de HHG y ATI para una gran variedad de sistemas atómicos y moleculares. Comparamos los resultados del MSFA con las soluciones numéricas de la ecuación de Schrödinger dependiente del tiempo (TDSE), cuando sea posible. Demostramos que nuestro modelo de MSFA puede ser utilizado para estudiar la física de los procesos fundamentales que están detrás de HHG y ATI. Con esta herramienta es posible investigar los procesos de interferencia, inherentes a todos los fenómenos de campo fuerte, en sistemas multi-céntricos. También es posible describir mediciones experimentales de difracción de electrones inducida por láser (LIED), permitiendo recuperar información estructural mediante el análisis de los espectros de fotoelectrones. Nuestro modelo abre el camino para estudiar los procesos de HHG y ATI en sistemas de moléculas complejas. Además tiene la potencialidad de poder ser fácilmente extendido para estudiar procesos de recombinación y dispersión, no sólo en moléculas grandes, sino también en sólidos.
8
Andrews, S. R. "Studies of double ionization and related electronic processes in molecules." Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635784.
Full textAbstract:
The major objective of these investigations was to develop a high-resolution double-charge-transfer spectrometer in order to measure vertical double-ionization energies of molecules, and to develop a thoeretical method to predict these energies economically. An overview of experimental techniques that have been used for the measurement of double-ionization energies is given in chapter 1; their advantages and restrictions are discussed and a brief review of double-charge-transfer spectroscopy studies to date is made. The various theoretical methods that are available for the studies of these processes are discussed in chapter 2, and a semi-empirical method based on the MSXα method is developed and tested for its effectiveness in predicting the complex singlet- and triplet-state energy distributions that exist in molecular dications; NH_3 and NO_2 were chosen for this purpose. Chapter 3 then describes in more detail the double-charge-transfer experiment, the spectrometers used in the studies presented in this thesis, and the modifications to that equipment. The next three chapters are devoted to the studies of double ionization of a wide variety of molecular dications. In chapter 4, theoretical predictions and interpretations of previous experimental results are presented; double-ionization energies of water, chloromethanes, iodomethanes and three metal hexacarbonyls (Cr, Mo, W) are predicted. This is followed in chapter 5 by joint theoretical and experimental studies initially of the triplet-state energies of ethane, allene and 1,1-dimethyl allene with the MS9 spectrometer, and then of ethyne, propyne and various alkyl-substituted amines with the high-resolution Finnigan 8230 spectrometer. The results are interpreted using the above semi-empirical theoretical technique. Finally, the possibility of studying singlet-state energies at high resolution is investigated in chapter 6, with joint experimental measurements and theoretical predictions of singlet-state energies of ethene, ethyne, propyne and allene being presented.
9
Al-Edhari, Ali Jaber. "Complex organic molecules in solar-type star forming regions." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY048/document.
Full textAbstract:
Le but de la présente thèse est l'étude de la compléxité moléculaire dans les régions de formation stellaires. Cette thèse s'axe sur deux classes de molécule aux caractéristiques prébiotiques : les molécules organiques complexes et les cyanopolyynes.Dans ce contexte, j'ai analysé des données d'un seul échantillon de relevés spec- traux en exploitant des codes de transfert radiatif à l'équilibre thermodynamique local (LTE) et/ou non-LTE pour deux sources : une proto-étoile de type solaire dans un environnement calme (IRAS 16293-2422) et un proto-ama constitué de proto-étoile de type solaire (OMC2-FIR4).L'objectif est de trouver des similar- ités et des différences entre ces deux cas.J'ai utilisé des données issu de deux relevés spectraux : TIMASSS (The IRAS16293-2422 Millimeter And Submilimeter Spectral Survey) réalisés en 2011 (Caux et al. 2011), et ASAI(Astrochemical Surveys At IRAM) réalisés pen- dant la période 2013-2015 (eg Lopez-Sepulcre et al.2015). J'ai extrais les lignes (identification et intensité intégrée) en utilisant le paquet disponible publique- ment : CASSIS (Centre d'Analyse Scientifique de Spectres Infrarouges et Sub- millimetrique). Pour finir, j'ai utilisé le paquet GRAPES (GRenoble Analysis of Protostellar Envelope Spectral) afin de modéliser la distribution spectrale énergétique de ligne (SLED) des molécules détectées, mais aussi afin d'estimer leurs abondances à travers l'envelope de IRAS16293 et du coeur chaud OMC2- FIR4.Les principaux résultats de la thèse sont :1. Le premier recensement complet des molecules organiques complexes (COMs) dans IRAS162932. La première détéction de COMs dans l'enveloppe froide d'une proto-étoile de type solaire (IRAS16293-2422) supportant l'idée qu'un méchanisme de formation, relativement efficace pour les COMs détectées, doit exister en phase gazeuse froide.3. La découverte d'une fine corrélation entre le diméthyle-éther (DME) et le méthyle-formate (MF) suggère une relation mère fille entre ces deux espèces.4. La detection de formamide, espèce avec un très fort potentiel prébiotique, dans plusieurs protoétoiles incluant IRAS16293-2422 et OMC2-FIR4.5. Le recensement complet des cyanopolyynes dans IRAS16293 et OMC2- FIR4 avec la détection de HC3N, HC5N, DC3N et pour OMC2-FIR4: le C13 isotopologue du HC3N cyanopolyynes.Ces résultats sont le sujet principal de deux publications (Jaber et al.2014, ApJ; Lopez-Sepulcre, Jaber et al.2015,MNRAS), un article accepté (Jaber et al., A & A) et un article à soumettre (Jaber et al. A & A)The present PhD thesis goal is the study of the molecular complexity in solar type star forming regions. It specifically focuses on two classes of molecules with a pre-biotic value, the complex organic molecules and the cyanopolyynes.At this scope, I analyzed data from single-dish spectral surveys by means of non-LTE or/and non-LTE radiative transfer codes in two sources, a solar type protostar in an isolated and quiet environment (IRAS16293-2422) and a proto-cluster of solar type protostars (OMC2-FIR4). The goal is to find similarities and differences between these two cases.I used data from two spectra surveys: TIMASSS (The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey), which has been carried out in 2011 (Caux et al. 2011), and ASAI (Astrochemical Surveys At IRAM), which has been carried out in 2013-2015 (e.g. Lopez-Sepulcre et al. 2015).I extracted the lines (identification and integrated intensity) by means of the publicly available package CASSIS (Centre dAnalyse Scientifique de Spectres Infrarouges et Submillimtriques).Finally, I used the package GRAPES (GRenoble Analysis of Protostellar Envelope Spectra) to model the Spectral Line Energy Distribution (SLED) of the detected molecules, and to estimate their abundance across the envelope and hot corino of IRAS16293-2422 and OMC2-FIR4, respectively.The major results of the thesis are:1) The first full census of complex organic molecules (COMs) in IRAS16293-2422;2) The first detection of COMs in the cold envelope of a solar type protostar (IRAS16293-2422), supporting the idea that a relatively efficient formation mechanism for the detected COMs must exist in the cold gas phase;3) The discovery of a tight correlation between the dimethyl ether (DME) and methyl format (MF), suggesting a mother-daughter relationship;4) The detection of formamide, a species with a very high pre-biotic value, in several protostars, included IRAS16293-2422 and OMC2-FIR4;5) The full census of the cyanopolyynes in IRAS16293-2422 and OMC2-FIR4, with the detection of HC3N and HC5N, DC3N and, for OMC2-FIR4, the 13C isotopologue of HC3N cyanopolyynes.These results are the focus of two published articles (Jaber et al. 2014, ApJ; Lopez-Sepulcre, Jaber et al. 2015, MNRAS), one accepted article (Jaber et al., A&A) and a final article to be submitted (Jaber et al., A&A)
10
Kowerko, Danny. "Dynamic Processes in Functionalised Perylene Bisimide Molecules, Semiconductor Nanocrystals and Assemblies." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-64194.
Full textAbstract:
Funktionalisierte organische Perylenbisimidfarbstoffe (PBI) und aus Cadmiumselenid bestehende Halbleiternanokristalle werden hinsichtlich physikalischer sowie chemischer Wechselwirkungsprozesse miteinander und mit ihrer Umgebung mittels zeitaufgelöster optischer Spektroskopie untersucht. Im Mittelpunkt der Studien an diesem organisch/anorganischen Modellsystem nanoskopischer Größe steht die Aggregatbildungskinetik und die Identifikation und Quantifizierung von Transferpozessen. Die Anbindung der gut löslichen PBI-Farbstoffe an die Oberfläche solcher Halbleiternanokristalle mittels spezieller Ankergruppen wird durch Selbstorganisation in Lösung realisiert. Die Kombination von Absorptions- und zeitaufgelöster Fluoreszenzspektroskopie zeigt einen unterschiedlich starken Einfluss von Liganden und Farbstoffen auf die Fluoreszenzlöschung der Nanokristalle und belegt, dass Resonanzenergietransfer zum Farbstoff nur in sehr geringem Maße die physikalische Ursache der Fluoreszenzlöschung ist. Die Anzahl adsorbierter Farbstoffe und die Stärke der Fluoreszenzlöschung eines einzelnen Farbstoffmoleküls werden aus zeitaufgelösten Einzelmolekülexperimenten an immobilisierten Emittern gewonnen, welche den direkten spektroskopischen Zugang zur Verteilung gebundener und freier Farbstoffe/Nanokristalle erlaubt. Darüber hinaus werden ankergruppen- und umgebungsspezifische Einflüsse auf die Konformations- und Orientierungsdynamik von Perylenbisimidmolekülen dargestellt. Abschließend werden photo-physikalische Gemeinsamkeiten chemisch unterschiedlich hervorgerufener Fluoreszenzlöschungsprozesse herausgearbeitet und im Kontext von Einzelkristall-Blinkprozessen diskutiert.
11
Schell, Felix [Verfasser]. "Sub-Femtosecond Processes in Molecules Studied by Coincidence Spectroscopy / Felix Schell." Berlin : Freie Universität Berlin, 2020. http://d-nb.info/1219070319/34.
Full text
12
Castrovilli, Mattea Carmen <1985>. "Elemetary processes of radiation damage in organic molecules of biological interest." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6386/1/Castrovilli_MatteaCarmen_tesi.pdf.
Full textAbstract:
It was observed in the ‘80s that the radiation damage on biological systems strongly depends on processes occurring at the microscopic level, involving the elementary constituents of biological cells. Since then, lot of attention has been paid to study elementary processes of photo- and ion-chemistry of isolated organic molecule of biological interest. This work fits in this framework and aims to study the radiation damage mechanisms induced by different types of radiations on simple halogenated biomolecules used as radiosensitizers in radiotherapy. The research is focused on the photofragmentation of halogenated pyrimidine molecules (5Br-pyrimidine, 2Br-pyrimidine and 2Cl-pyrimidine) in the VUV range and on the 12C4+ ion-impact fragmentation of the 5Br-uracil and its homogeneous and hydrated clusters.
Although halogen substituted pyrimidines have similar structure to the pyrimidine molecule, their photodissociation dynamics is quite different. These targets have been chosen with the purpose of investigating the effect of the specific halogen atom and site of halogenation on the fragmentation dynamics. Theoretical and experimental studies have highlighted that the site of halogenation and the type of halogen atom, lead either to the preferential breaking of the pyrimidinic ring or to the release of halogen/hydrogen radicals. The two processes can subsequently trigger different mechanisms of biological damage.
To understand the effect of the environment on the fragmentation dynamic of the single molecule, the ion-induced fragmentation of homogenous and hydrated clusters of 5Br-uracil have been studied and compared to similar studies on the isolated molecule.
The results show that the “protective effect” of the environment on the single molecule hold in the homogeneous clusters, but not in the hydrated clusters, where several hydrated fragments have been observed. This indicates that the presence of water molecules can inhibit some fragmentation channels and promote the keto-enol tautomerization, which is very important in the mutagenesis of the DNA.
13
Castrovilli, Mattea Carmen <1985>. "Elemetary processes of radiation damage in organic molecules of biological interest." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6386/.
Full textAbstract:
It was observed in the ‘80s that the radiation damage on biological systems strongly depends on processes occurring at the microscopic level, involving the elementary constituents of biological cells. Since then, lot of attention has been paid to study elementary processes of photo- and ion-chemistry of isolated organic molecule of biological interest. This work fits in this framework and aims to study the radiation damage mechanisms induced by different types of radiations on simple halogenated biomolecules used as radiosensitizers in radiotherapy. The research is focused on the photofragmentation of halogenated pyrimidine molecules (5Br-pyrimidine, 2Br-pyrimidine and 2Cl-pyrimidine) in the VUV range and on the 12C4+ ion-impact fragmentation of the 5Br-uracil and its homogeneous and hydrated clusters.
Although halogen substituted pyrimidines have similar structure to the pyrimidine molecule, their photodissociation dynamics is quite different. These targets have been chosen with the purpose of investigating the effect of the specific halogen atom and site of halogenation on the fragmentation dynamics. Theoretical and experimental studies have highlighted that the site of halogenation and the type of halogen atom, lead either to the preferential breaking of the pyrimidinic ring or to the release of halogen/hydrogen radicals. The two processes can subsequently trigger different mechanisms of biological damage.
To understand the effect of the environment on the fragmentation dynamic of the single molecule, the ion-induced fragmentation of homogenous and hydrated clusters of 5Br-uracil have been studied and compared to similar studies on the isolated molecule.
The results show that the “protective effect” of the environment on the single molecule hold in the homogeneous clusters, but not in the hydrated clusters, where several hydrated fragments have been observed. This indicates that the presence of water molecules can inhibit some fragmentation channels and promote the keto-enol tautomerization, which is very important in the mutagenesis of the DNA.
14
Vichetti, Rafael Mário. "Síntese dos isótopos do monóxido de carbono no meio interestelar /." Rio Claro : [s.n.], 2009. http://hdl.handle.net/11449/91889.
Full textAbstract:
Orientador: Carmen Maria AndreazzaBanca: Edson Denis Leonel
Banca: José Williams dos Santos Vilas Boas
Resumo: De acordo com os resultados observacionais de condensações de nuvens moleculares escuras, grandes variações na razão 13CO/C18O são observadas quando se comparam os resultados obtidos nas condensações situadas dentro da mesma nuvem, bem como de nuvem para nuvem. O valor médio dessa razão na condensação principal de Ophiuchus é inferior a 5. Por outro lado, o valor encontrado nas condensações que estão situadas ao norte de Oph é maior que 10. Grandes diferenças também são encontradas quando se comparam os resultados observacionais de diferentes nuvens escuras, tais como Ophiuchus e Taurus, onde são observados também um decréscimo da razão C18O/C17O com o aumento da densidade. Os processos químicos e físicos que governam essas variações ainda não estão claros. Nesse sentido, o objetivo da presente proposta é analisar a influência do colapso gravitacional de condensações de nuvens moleculares escuras na síntese das moléculas CO, C17O, C18O, 13CO, 13C17O e 13C18O. Tal análise é feita com base em comparações entre modelos que consideram diferentes condições entre si, tais como, tamanho da cadeia química, velocidade de colapso, densidade inicial e processos de congelamento de espécies químicas na superfície de grãos de poeira. Os resultados obtidos mostram que o tamanho da cadeia química tem influência nas razões 13CO/C18O e C18O/C17O, mas não tanto quanto a densidade inicial e a velocidade do colapso. Além disso, o congelamento das espécies químicas nos grãos é mais significativo nos estágios mais avançados da evolução da condensação. Os modelos de condensações escuras que sofrem colapso gravitacional lento e em queda livre reproduzem satisfatoriamente as razões 13CO/C18O e C18O/C17O observadas, o que permite concluir que o colapso gravitacional pode ter um importante efeito nas referidas razões.
Abstract: According to the observational results of dark molecular clouds condensations, large variations in the ratio 13CO/C18O are observed when comparing the results obtained in the condensations located within the same cloud and cloud to cloud. The average value of this ratio in the main condensation of Ophiuchus is below 5. On the other hand, the value found in the condensations that are located north of Oph is larger than 10. Large differences are also found when comparing the observational results of different dark clouds such as Ophiuchus and Taurus, in which are also found a decrease of the C18O/C17O ratio with increasing density. The chemical and physical processes that govern these variations are still unclear. In this sense, the objective of this proposal is to analyze the influence of the gravitational collapse of centrally condensed clumps of dense molecular gas in the synthesis of the CO, C17O, C18O, 13CO, 13C17O and 13C18O molecules. This analysis is based on comparisons among models that consider different condition, such as, chemical chain, initial density, speed of collapse and freezing processes of the chemical species on the surface of dust grains. The results show that the size of the chemical chain has influence on the 13CO/C18O and C18O/C17O ratios, but they are not as important as the initial density and the speed of the collapse. Furthermore, the freezing of chemical species on the grains occurs at later times of the collapse. The models of a gravitational free-fall collapsing core and of slowly contracting core with higher initial density are consistent with observations. These results indicate that the gravitational collapse of molecular cores can have an important effect in the 13CO/C18O and C18O/C17O ratios.
Mestre
15
Kilic, Hamdi Sukur. "Comparison of nanosecond and femtosecond laser mass spectrometry." Thesis, University of Glasgow, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362940.
Full text
16
Zhang, Wenzhu. "Oscillator strengths for photoabsorption and photoionization processes of feron and NO₂ molecules." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/32006.
Full textAbstract:
Absolute photoabsorption differential oscillator strengths (cross sections) for N Is and 0 Is inner shell excitation and ionization of N0₂ have been derived from the presently obtained high resolution electron energy loss spectra using dipole (e,e) spectroscopy. The N0₂ inner shell differential oscillator strength spectra are in good agreement with multichannel
quantum defect theory calculations in both excitation energies and (differential) oscillator strengths. The N0₂ spectra were interpreted with the aid of the calculations. A resonance present in both the N0₂ N Is and 0 Is ionization continua was identified as excitation to an unbound molecular orbital. A consideration of the present spectra for N0₂ and earlier spectra for other molecules showed that additional prominent structures observed in previously reported N0₂ inner shell photoabsorption spectra obtained using synchrotron radiation were due to the presence of impurities.
Absolute photoabsorption differential oscillator strengths for the valence shells of CF₄, CF₃CI, CF₂Cl₂ and CFCI₃ have been measured in the equivalent photon energy range up to 200 eV using dipole (e,e) spectroscopy. The present results are in good agreement with earlier reported optical measurements and electron impact measurements. The photoionization efficiencies and also the photoion branching ratios have been determined for CF₄, CF₃CI, CF₂C1₂ and CFCI₃ from time of flight mass spectra using dipole (e,e+ion) coincidence spectroscopy at equivalent photon energies ranging up to 80 eV. Absolute partial differential oscillator strength spectra for the molecular and dissociative photoions have been derived. The natures of the dipole induced breakdown pathways of CF₄, CF₃CI and CF₂C1₂ were investigated by combining the present differential oscillator strength
measurements for molecular and dissociative photoionization with photoelectron data obtained in the present thesis work plus previously reported photoelectron branching ratios. On the basis of the present work, a revised set of absolute electronic state partial photoionization differential oscillator strengths for CF₄ are presented.
Absolute electronic state partial photoionization differential oscillator strength spectra
for CF₃CI, CF₂C1₂ and CFCI₃ in the photon energy range 41—160 eV have been derived by combining total differential oscillator strength spectra obtained in the present thesis work with photoelectron branching ratios obtained from photoelectron spectra measured using synchrotron radiation.
Absolute photoabsorption differential oscillator strengths and for F Is, C Is, and Cl 2p,2s inner shell excitation and ionization of freon molecules CF₄, CF₃C1, CF₂C1₂, CFCI₃ and CCl₄ have been derived from the presently obtained high resolution electron energy loss spectra plus previously reported. Tentative assignments of the spectra were obtained using the MO picture and the potential barrier model.Science, Faculty of
Chemistry, Department of
Graduate
17
Marchione, Demian. "Thermal and non-thermal processes of simple molecules on model interstellar ices." Thesis, Heriot-Watt University, 2015. http://hdl.handle.net/10399/3010.
Full textAbstract:
Thin film growth and desorption behaviour of simple molecules have been studied by means of surface science techniques, such as mass spectrometry and reflectionabsorption infrared spectroscopy (RAIRS), in order to understand the physiochemical processes and intermolecular interactions in model interstellar ices. The systems of interest comprise a silica surface, representing the bare grains in the interstellar medium, and films of water (H2O), methanol (CH3OH), diethyl ether ((CH3CH2)2O) and benzene (C6H6). While H2O and CH3OH are key components of the icy mantles, (CH3CH2)2O and C6H6 are found in lower abundances being two products, among many, of the rich chemistry occurring in these environments. Temperature programmed desorption and IR signatures of pure solid H2O, CH3OH, and (CH3CH2)2O adsorbed on amorphous silica were compared as a function of surface coverage and temperature. H2O and (CH3 CH2)2O display opposite behaviours, consistent with two-dimensional island formation and wetting of the amorphous silica surface respectively. CH3OH, being intermediate between the two species, exhibited aspects of both behaviours. Temperature programmed RAIRS has revealed evidence for thermal activation of di↵usion of H2O over the amorphous silica surface between 40 K and 60 K, and of CH3OH between 20 K and 40 K, while no conclusive evidence was found for such with (CH3CH2)2O. Experiments have been performed to study the thermal desorption and the IR features of C6H6 on CH3OH and (CH3CH2)2O solids in comparison to those on a solid H2O substrate at 110 K. The results give a clear picture of the C6H6 film growth from low to high coverages. Ab initio quantum chemical calculations highlight the key interactions between the two species for each system, C6H6/H2O, C6H6/CH3OH and C6H6/(CH3CH2)2O, in support of the interpretation of the data. Building on this basis, 250 eV electron irradiation of C6H6 on thick ices of H2O, or CH3OH, or (CH3CH2)2O was investigated to demonstrate the crucial role of hydrogen-bonding in propagating electronic excitation to the solid-vacuum interface where C6H6 desorption can occur. Competitive electron-induced chemistry in the form of molecular hydrogen (H2) formation was also observed. The electron beam used in the these experiments is inelastically scattered by the molecules in the solid ices forming a similar flux of electrons to that associated to cosmic rays. Conclusions related to the impact of these observations on the early phase of icy interstellar grain chemistry are discussed.
18
Zapata, Abellán Felipe. "Electron dynamics induced by single and multiphoton processes in atoms and molecules." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS431.
Full textAbstract:
Cette thèse contribue aux développements de méthodes numériques utilisées pour reproduire la dynamique électronique induite par des processus à un et plusieurs photons dans les atomes et molécules. Dans le domaine perturbatif, la photoexcitation et la photoionisation ont été étudiées à l'aide de la théorie de la fonctionnelle de la densité à séparation de portée, dans le but de prendre en compte les effets d'interaction électron-électron. De plus, dans le domaine non-perturbatif, les spectres au-delà du seuil d'ionisation et les spectres de génération d'harmoniques d'ordres élevés ont été simulés en utilisant différentes représentations de la fonction d'onde dépendante du temps du système étudié. Cette étude ouvre la possibilité d'explorer des processus matière-rayonnement dans des systèmes plus complexesThe present PhD thesis contributes to the development of numerical methods used to reproduce the electron dynamics induced by single and multiphoton processes in atoms and molecules. In the perturbative regime, photoexcitation and photoionization have been studied in atoms with range-separated density-functional theory, in order to take into account the electron-electron interaction effects. Moreover, in the non-perturbative regime, above-threshold ionization and high-harmonic generation spectra have been simulated using different representations for the time-dependent wave function for the purpose of describing the continuum states of the irradiated system. Our studies open the possibility of exploring matter-radiation processes in more complex systems
19
Schröder, Benjamin. "Theoretical high-resolution spectroscopy for reactive molecules in astrochemistry and combustion processes." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://hdl.handle.net/21.11130/00-1735-0000-0005-12DA-1.
Full text
20
Cruz, Rodriguez Lidice. "Méthodes de dynamique quantique ultrarapide basées sur la propagation de trajectoires." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30254/document.
Full textAbstract:
Dans cette thèse, différentes méthodes de dynamique quantique basées sur la propagation de trajectoires sont développées. La première approche consiste en une développer global des champs hydrodynamiques sur une base de polynômes de Chebyshev. Ce schéma est utilisé pour étudier la dynamique vibrationnelle unidimensionnelle de paquets d'ondes dans des potentiels harmoniques et anharmoniques. Par la suite, une méthodologie différente est développée, qui, à partir d'un paramétrage précédemment proposé pour la densité quantique, permet de construire des potentiels d'interaction effectifs entre les pseudo-particules représentant la densité. Dans le cadre de cette approche, plusieurs problèmes de modélisation sont étudiés et des effets quantiques importants sont décrits, tels que l'énergie de point zéro, l'effet tunnel, la diffusion et la réflexion sur une barrière. La même approximation est utilisée pour l'étude de l'ionisation des atomes par laser. Dans une troisième approche, un potentiel quantique approximatif à plusieurs corps est dérivé pour décrire des matrices d'argon et de krypton contenant une impureté de sodium. Il est obtenu en proposant un ansatz approprié pour la fonction d'onde de l'état fondamental du solide. Le potentiel est utilisé dans les simulations de dynamique moléculaire pour obtenir les spectres d'absorption de l'atome de Na isolé dans les matrices cryogéniquesIn this thesis different trajectory-based methods for the study of quantum mechanical phenomena are developed. The first approach is based on a global expansion of the hydrodynamic fields in Chebyshev polynomials. The scheme is used for the study of one-dimensional vibrational dynamics of bound wave packets in harmonic and anharmonic potentials. Furthermore, a different methodology is developed, which, starting from a parametrization previously proposed for the density, allows the construction of effective interaction potentials between the pseudo-particles representing the density. Within this approach several model problems are studied and important quantum mechanical effects such as, zero point energy, tunneling, barrier scattering and over barrier reflection are founded to be correctly described by the ensemble of interacting trajectories. The same approximation is used for study the laser-driven atom ionization. A third approach considered in this work consists in the derivation of an approximate many-body quantum potential for cryogenic Ar and Kr matrices with an embedded Na impurity. To this end, a suitable ansatz for the ground state wave function of the solid is proposed. This allows to construct an approximate quantum potential which is employed in molecular dynamics simulations to obtain the absorption spectra of the Na impurity isolated in the rare gas matrix
21
Handt, Jan. "Ab-initio molecular dynamics studies of laser- and collision-induced processes in multielectron diatomics, organic molecules and fullerenes." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-62279.
Full textAbstract:
This work presents applications of an ab-initio molecular dynamics method, the so-called nonadiabatic quantum molecular dynamics (NA-QMD), for various molecular systems with many electronic and nuclear degrees of freedom. Thereby, the nuclei will be treated classically and the electrons with time-dependent density functional theory (TD-DFT) in basis expansion. Depending on the actual system and physical process,
well suited basis sets for the Kohn-Sham orbitals has to be chosen. For the ionization process a novel absorber acting in the energy space as well as additional basis functions will be used depending on the laser frequency.
In the first part of the applications, a large variety of different laser-induced molecular processes will be investigated. This concerns, the orientation dependence of the ionization of multielectronic diatomics (N2, O2), the isomerization of organic molecules (N2H2) and the giant excitation of the breathing mode in fullerenes (C60).
In the second part, fullerene-fullerene collisions are investigated, for the first time in the whole range of relevant impact velocities concerning the vibrational and electronic energy transfer (\"stopping~power\").
For low energetic (adiabatic) collisions, it is surprisingly found, that a two-dimensional, phenomenological collision model can reproduce (even quantitatively) the basic features of fusion and scattering observed in the fully microscopic calculations as well as in the experiment.
For high energetic (nonadiabatic) collisions, the electronic and vibrational excitation regimes are predicted, leading to multifragmentation up to complete atomization.
22
GORNATI, DAVIDE. "RATIONAL DESIGN AND SYNTHESIS OF SMALL MOLECULES TARGETED AGAINST NEURODEGENERATIVE PROCESSES AND DISEASES." Doctoral thesis, Università degli Studi di Milano, 2019. http://hdl.handle.net/2434/606993.
Full textAbstract:
Improved sanitary conditions, disease prevention (e.g., vaccinations) and treatment (e.g., antibiotics) have increased life expectancy, up to the 67.2 years value in 2010. Unfortunately, living longer a poor life does not represent anyone’s dream, mostly due to neurodegenerative diseases (NDDs). Alzheimer’s Disease International (ADI) estimates in its 2013 report that there are more than 35 million people with dementia worldwide as of 2010, and that this number will double by 2030 and triplicate by 2050. In industrialized countries the prevalence of Parkinson’s disease (PD) is about 1% for people over 60, with estimates of up to 4% for people in the highest age groups. In 2016 the Centres for Disease Control and Prevention estimated that between 14,000 - 15,000 Americans suffered from Amyotrophic Lateral Sclerosis (ALS).
These and other NDDs are the result of neurodegenerative processes, that entail the progressive loss of structure or function of neurons, eventually causing their death. Symptomatic treatment strategies available on the market for NDDs are inadequate, as they offer only temporary relief without changing the ultimate NDD outcome.
Effective treatment of NDDs should be based on small molecules able to modulate disease-modifying pathways involved in the development and/or the progression of NDDs, to cause their remission. In my Ph.D. work I focused on four different pathways (each described in a dedicated Chapter) involved in the development of multiple NDDs. With the aim to therapeutically modulate them by promoting and/or inhibiting those targets, I’ve rationally designed and synthetized several classes of compounds. My research group established a multi-disciplinary approach in collaboration with bioinformatics, biologists, pharmacologists and clinicians; thus, my putative NDD treatments were tested by our collaborators in different Universities and Institutes (CIBIO, University of Trento; San Raffaele Research Institute, Milan; Department of Neuroscience, Federico II University, Naples).
23
Gattupalli, Rajeswar R. "Advances in global optimization /." View online ; access limited to URI, 2008. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3314454.
Full text
24
Oguz, Cihan. "Control-oriented modeling of discrete configuration molecular scale processes applications in polymer synthesis and thin film growth /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19867.
Full textAbstract:
Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Gallivan, Martha A.; Committee Member: Hess, Dennis; Committee Member: Lee, Jay H.; Committee Member: Li, Mo; Committee Member: Ludovice, Pete.
25
Hedin, Lage. "Studies of Single and Multiple Ionization Processes in Rare Gases and some Small Molecules." Doctoral thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-221128.
Full textAbstract:
In this thesis various aspects of photoionization are investigated with respect to both single and multiple electron emission from atoms and molecules. The studies include both valence and core levels and involve transitions which leave the atoms or molecules in various charge states. S2p electrons in the CS2 molecule were excited into Rydberg orbitals close to the ionization threshold. Subsequent autoionization leads to the emission of single electrons which were detected by a conventional electron spectrometer, bringing the molecule into various cationic states characterized by two valence holes and a Rydberg spectator electron. Vibrational progressions have been assigned as excitations of the totally symmetric v1 and the asymmetric stretching v3 modes in the cationic states. Double ionization spectra of the CS2 molecule were recorded in the S2p and C1s innershell ionization regions using a magnetic bottle many-electron coincidence spectrometer, revealing dicationic states formed out of one inner-shell vacancy and one vacancy in the valence region. The spectrum connected to the S2p vacancy is richly structured in contrast to the spectrum connected to the C1s vacancy, which shows essentially one distinct band. The development of a new variant of the magnetic bottle coincidence technique tailored for valence triple photoionization studies of rare gas atoms at synchrotron radiation sources is presented, overcoming the problem of high repetition rate in single-bunch operation of the storage ring. The studies of the rare gas atoms confirm that a correction of the lowest triple-ionization energy of Kr, currently listed in standard tables, is needed. Also, single-site N1s and O1s double core ionization of the NO and N2O molecules and single-site O1s, C1s and S2p double core ionization of the OCS molecule has been studied with the magnetic bottle technique. Double core holes are of particular interest due to putatively larger chemical shifts compared to single core holes. The observed ratio between the double and single ionization energies are in all cases close or equal to 2.20.
26
Yamazaki, Shohei. "A method for locating conical intersection in solvated molecules and application to photochemical processes." 京都大学 (Kyoto University), 2007. http://hdl.handle.net/2433/136734.
Full text
27
Schröder, Benjamin [Verfasser]. "Theoretical high-resolution spectroscopy for reactive molecules in astrochemistry and combustion processes / Benjamin Schröder." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://d-nb.info/1216330557/34.
Full text
28
McQuilken, Andrew Lynn. "Some pulsed IR and UV studies of vibrational energy transfer processes in selected triatomic molecules." Thesis, Queen's University Belfast, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336132.
Full text
29
Skolimowska, Ewelina Szymanska. "Dissociative electron attachment and dipolar dissociation processes in organic molecules found in the interstellar medium." Thesis, Open University, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606955.
Full textAbstract:
In this thesis, the results of a series of experimental studies of electron induced anion formation are presented for a number of molecular targets. The motivation of this work was the discovery of anions in interstellar space and in planetary atmospheres raising the question of how such species are formed. Molecular anions are commonly formed by electron impact via the Dissociative Electron Attachment (DEA) and Dipolar Dissociation (DD) with the simultaneous formation of neutral often reactive species (in case of DEA) and cationic fragments (in case of DD). These fragments may then undergo reactions leading to the chemical synthesis of larger stable products. Thus electron induced chemistry may provide a hitherto unexplored route of molecular synthesis and aid in our understanding of the role of anions in interstellar and atmospheric chemistry. .
30
Zhou, Luwenjia. "Probing the processes driving distant and local star-formation in galaxies through dust and molecules." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP099.
Full textAbstract:
Les études sur l'évolution des galaxies ont été révolutionnées au cours des dernières décennies grâce aux nouveau télescopes et aux instruments de pointe. Les interféromètres Herschel, ALMA et NOEMA permettent d'observer l'émission des poussières tracant la formation des étoiles, invisible dans les bandes infrarouges proche observées par les télescopes optiques. Dans cette thèse, je me concentre sur la formation des étoiles aux grandes échelles des galaxies (~kpc). En utilisant les données des téléscopes Herschel, ALMA, NOEMA, et SAMI IFU, ma thèse tente de mettre en lumière les questions suivantes : (1) Comment les premières galaxies ont-elles formé des étoiles à partir du gaz contenant peu de métaux ? (2) Comment les galaxies massives du début de l'Univers ont-elles rapidement constitué leur masse et finalement cessé de former des étoiles ? (3) Quel est le rôle joué par les environnements dans lesquels elles résident ? (4) Comment la rétroaction de la formation des étoiles affecte-t-elle la cinématique des galaxies ? Premièrement, je présente l'étude de six galaxies optiquement sombres extraites de l'étude GOODS-ALMA (la plus grande étude cosmologique à 1,1m) dont le décalage vers le rouge est supérieur à z=3. Je présente des preuves que quatre d'entre elles appartiennent à la même surdensité de galaxies, situé à z~3.5. L'une d'entre elles, AGS24, est la galaxie la plus massive, sans noyau galactique actif et situé à z>3. Cette dernière se situe également au centre du pic de densité de surface des galaxies, suggèrant que la surdensité environnante est un proto-amas en cours de virialisation et qu'AGS24 est un candidat progéniteur d'un futur amas de galaxie plus brillant. Deuxièmement, en me basant sur une observation NOEMA, j'ai étudié la teneur en gaz moléculaire dans IZw18, l'une des galaxies les plus pauvres en métal de l'Univers local. J'ai obtenu une limite supérieure d'émission de CO(J=2-1) qui est dix fois plus faible que précédemment déterminée, ceci malgré la forte activité de formation d'étoiles. Sa faible teneur en CO (par rapport à sa luminosité infrarouge), son taux de formation d'étoiles, et sa luminosité [CII] indiquent un changement drastique dans la structure du MIS (environ quelques pourcents de la métallicité solaire). En particulier, la luminosité élevée [CII] par rapport au CO implique un réservoir moléculaire plus important que l'émetteur de CO dans l'IZw18. Troisièmement, mes travaux sur les sources d'énergie des mouvements turbulents montrent qu'à des échelles inférieures au kpc, les galaxies locales formant des étoiles du relevé SAMI présentent une distribution plate de la dispersion de vitesse du gaz ionisé en fonction de la densité de surface du taux de formation d'étoiles. Cependant, le plancher de dispersion de vitesse est plus élevé que ce que prédisent les modèles "feedback-driven". Cela suggère que des sources supplémentaires à la rétroaction de formation d'étoiles entraînent des mouvements aléatoires du MIS dans les galaxies formant des étoiles.Enfin, je présente mes travaux sur l'émission de poussières spatiallement résolue des galaxies extrêmement pauvres en métaux observées par Herschel. Ces galaxies présentent des températures de poussière plus élevées et des indices d'émissivité plus faibles que ceux des galaxies spirales. Environ la moitié de l'émission à 100um provient de la poussière chaude (50K), par opposition à la composante froide (~20K) de la poussière. Les couleurs de l'infrarouge lointain sont toutes liées aux densités de surface des jeunes étoiles, mais pas aux densités de surface des masses stellaires. Cela suggère que leur poussière (70~350μm) est principalement chauffée par le rayonnement des jeunes étoilesStudies on galaxy evolution have been revolutionized during the last decade thanks to the state-of-the-art telescopes and instruments. Herschel Space Telescope, ALMA and NOEMA interferometers can observe the dust emission that traces star formation missed by optical to near-infrared telescopes. Their high sensitivity pushes further their detections to the most distant galaxies or the faintest local galaxies, of which the formation and evolution challenge current theories and models. And the integral field unit technique combines the spatial information with the properties extracted from spectra which allows a thorough study of galaxy kinematics. In this thesis, I focus on the large-scale (~kpc) star formation of galaxies. Taking advantage of the data from Herschel, ALMA, NOEMA, and the SAMI IFU survey, my thesis tries to put more constraints on the following questions: (1) How did the first galaxies form stars out of gas with little metal? (2) How did the massive galaxies in the early Universe rapidly build up their masses and finally stop forming stars? and (3) what is the role played by the environments they reside in? (4) How does star formation feedback affect the galaxy kinematics? A large portion of the work done in this thesis is based on the GOODS-ALMA survey, the largest cosmological survey with the large ALMA interferometer at 1.1 mm. I studied the six optically dark galaxies with redshifts greater than z =3 uncovered by this survey. We present evidence that four out of the six optically dark galaxies belong to the same overdensity of galaxies at z~3.5. One of them, AGS24, is the most massive galaxy without an active galactic nucleus at z >3 in the GOODS-ALMA field. It also falls in the very center of the galaxy surface density peak, suggesting that the surrounding overdensity is a proto-cluster in the process of virialization and that AGS24 is the candidate progenitor of the future brightest cluster galaxy. I also studied the molecular gas content in IZw18, one of the most metal poor galaxies in the local Universe based on the observation of NOEMA. I obtain an upper limit of CO J =2-1 emission, which is used as a tracer of molecular gas, to be ten times lower than previous studies despite its vigorous star formation activities. Such low CO content relative to its infrared luminosity, star formation rate and [CII] luminosity, indicates a drastic change in the structure of the ISM at around a few percentages of Solar metallicity. Especially, the high [CII] luminosity relative to CO implies a larger molecular reservoir than the CO emitter in IZw18. My work on the energy sources of the turbulent motions shows that on sub-kpc scales, local star-forming galaxies from the SAMI survey display a flat distribution of ionized gas velocity dispersion as a function of star formation rate surface density. However, the velocity dispersion floor is higher than predicted by feedback-driven models. This suggests that additional sources to star formation feedback drive random motions of the interstellar medium in star-forming galaxies. Finally I present my work on the spatially resolved dust emission of extremely metal-poor galaxies observed by Herschel. These galaxies show higher dust temperatures and lower emissivity indices compared to those of spiral galaxies. And about half of the emission at 100μm comes from warm (50,K) dust, in contrast to the cold (~20K) dust component. The far-infrared colours are all related to the surface densities of young stars, but not to the stellar mass surface densities. This suggests that their dustemission (70~350μm) is primarily heated by radiation from young stars
31
Paiva, Rafael Rothganger de. "Two-photon two-atom processes." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-24102013-080238/.
Full textAbstract:
In the atomic, molecular, optical physics field, processes involving two photons are very well understood and used in applications ranging from spectroscopy to laser cooling technics. In this thesis is presented the study and experimental realization of two two-photon processes. Using sodium atoms trapped in a magnetic optical trap we could demonstrate two-photon cooperative absorption, and that the creation of a molecular bound state using only light fields, or photonic bound state, is possible. Two-photon cooperative absorption, very common in solid-state physics, is a process where a pair of atoms initially in the ground state is excited to the double excited state, via absorption of two photons with frequecy that is not ressonant with any excited state. Its experimental realization with cold atoms may open new and exciting possibilities to better understand nonlinear effects, and it is a new way to create correlated atoms and photons in cold atomic physics. This absorption was observed by ionization of the pair after the excitation. A simple model that considers only dipole-dipole interactions between the atoms allows us to understand the basic features observed in the experimental data. A photonic bound state uses two photons to create the two basic features of a molecular bound state: a repulsive part and an attractive part. A blue photon, blue detuned from the atomic transition, connects the ground state of the pair to the repulsive part of the first excited molecular state 1, and a red photon, red detuned from the atomic transition, connects the connects the ground state of the pair to the attractive part of the first excited molecular state. In the dressed state picture, when the light fields are strong, this three-states-two-photon system creates adiabatic bound potentials that are strongly dependent of the photon properties. Using a theoretical model we could study how this bound energies changes when we change the photon properties, and the experimental data shows that this photos are indeed dressing the potentials with a efficiency that would enable the creation of photonic molecules.No campo da física atômica, molecular e ótica processos envolvendo dois fótons são bem compreendidos e usados em diversas aplicações. Nesta tese apresentamos o estudo e a realização experimental de dois processos de dois-fótons. Usando átomos de sódio aprisionados em uma armadilha magneto ótica, demonstramos a absorção cooperativa de dois fótons e que a criação de um estado ligado molecular usando somente campos de luz, ou estado ligado fotônico, é possível. Absorção cooperativa de dois fótons, um processo bem comum em física de estado sólido, acontece quando um par de átomos inicialmente no estado fundamental é excitado para o estado duplamente excitado, via absorção de dois fótons de frequência não ressonante com a dos estados excitado. A realização experimental deste processo em um sistema de átomos frios pode abrir novas, e excitantes possibilidades para entender melhor processos não lineares, e é um novo método de criar átomos e fótons correlacionados. Essa absorção foi observada através da ionização do par depois da absorção, e um modelo simples que considera somente interação dipolo-dipolo entre os dois átomos nós ajuda entender as características básicas dos dados obtidos. Um estado ligado fotônico usa dois fótons para criar as duas características básicas dos estados ligados moleculares: a parte repulsiva e a parte atrativa. Um fóton azul, deslocado para o azul da transição atômica, conecta o estado fundamental do par a parte repulsiva do primeiro estado excitado molecular 1, e um fóton vermelho, deslocado para o vermelho da transição atômica, conecta o estado fundamental a parte atrativa do deslocado para o azul da transição atômica. No contexto de estados vestidos, quando os campos de luz são intensos, esse sistema de três estados e dois fótons cria potenciais ligantes adiabáticos que são fortemente dependentes das propriedades desses fótons. Usando um modelo teórico para esses potenciais pudemos estudar como é essa dependência, com as características do fótons, e os dados experimentais mostram que esses fótons estão de fato vestindo os estados com uma eficiência que viabiliza a criação de moléculas fotônicas.
32
Leitner, Torsten [Verfasser], and Wolfgang [Akademischer Betreuer] Eberhardt. "Ultrafast processes in molecules visualized with femtosecond pump-probe photoelectron spectroscopy / Torsten Leitner. Betreuer: Wolfgang Eberhardt." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/1029192677/34.
Full text
33
Loukova, G. V., V. V. Vasiliev, V. L. Ivanov, M. Ya Melnikov, V. A. Smirnov, and E. E. Melnichuk. "Two−photon Processes in Organometallic Molecules and Clusters: T−T Absorption of Group IV Metal Complexes." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35395.
Full textAbstract:
Triplet – triplet absorption of d0 metal complexes was for the first time revealed and studied by means of pulse photolysis and electron-exchange (Dexter) resonant energy transfer energy transfer.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35395
34
Kocić, Nemanja [Verfasser], and Jascha [Akademischer Betreuer] Repp. "Dynamic and static charging processes of single molecules - A scanning probe study / Nemanja Kocić ; Betreuer: Jascha Repp." Regensburg : Universitätsbibliothek Regensburg, 2018. http://d-nb.info/1149920343/34.
Full text
35
Goulart, Marcelo Moreira. "Espectrometria de massa a temperaturas próximas a 0 K e simulações em mecânica molecular no estudo de espécies de interesse astrofísico e astroquímico." Universidade Federal de Juiz de Fora, 2014. https://repositorio.ufjf.br/jspui/handle/ufjf/433.
Full textAbstract:
Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-01-19T14:05:14Z
No. of bitstreams: 1
marcelomoreiragoulart.pdf: 10308658 bytes, checksum: f8584bc8a12f11d188a8cdb968acd85d (MD5)Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-01-25T17:58:35Z (GMT) No. of bitstreams: 1 marcelomoreiragoulart.pdf: 10308658 bytes, checksum: f8584bc8a12f11d188a8cdb968acd85d (MD5)
Made available in DSpace on 2016-01-25T17:58:35Z (GMT). No. of bitstreams: 1 marcelomoreiragoulart.pdf: 10308658 bytes, checksum: f8584bc8a12f11d188a8cdb968acd85d (MD5) Previous issue date: 2014-10-24
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Alcoóis e fulerenos estão entre as espécies atualmente observadas no meio interestelar (MI). Metanol é, dentre as espécies encontradas no espaço, uma das mais estudadas e sua importância como molécula orgânica é bem conhecida. A molécula de fulereno (carbono 60) pode ser responsável por carrear compostos entre diferentes regiões do espaço e pode, também, servir como matriz de reação para moléculas orgânicas tais como alcoóis. A investigação de possíveis reações químicas envolvendo diferentes compostos no MI pode auxiliar a compreensão a respeito da formação e transporte de moléculas no universo. Neste tese foram realizados experimentos nos quais aglomerados puros de metanol, etanol e também aglomerados de C60 dopados com estes alcoóis foram formados a partir da captura individual de moléculas por gotículas de He superfluido com temperatura isotérmica de 0,37 K atingida através de resfriamento evaporativo de átomos de Hélio (He). Após a captura os aglomerados foram ionizados por um feixe de elétrons de 70 eV e acelerados através de um conjunto de lentes eletrostáticas em direção a um analizador por tempo de vôo (TOF) onde o rendimento iônico foi obtido como função da razão massa sobre carga. Cálculos de mecânica molecular com a utilização do campo de forças MM2 e também simulações utilizando dinâmica molecular foram realizadas para interpretar os espectros obtidos. Nesta tese reportamos uma reação química ocorrendo no interior dos aglomerados após o processo de ionização, onde as moléculas de álcool sofrem desidratação, formando água (H2O), éteres dimetílico e dietílico e possivelmente eteno. Há evidências de que a reação é iniciada por um próton advindo da fragmentação de uma das moléculas alcoólicas devido ao processo de ionização. As moléculas de éter tendem a deixar o aglomerado após sua formação enquanto as moléculas de água permanecem no interior, solvatadas por alcoóis. Números mágicos são também observados nos espectros para diferentes números de moléculas de C60 e alcoóis.
Alcohols and fullerenes are among the species observed in the interstellar medium (ISM) to date. Methanol is one of the most studied molecules detected in space and its importance as an organic molecule is well known. The fullerene molecule (carbon 60) could be responsible for carrying compounds along different regions of space and could also serve as a reaction matrix for organic molecules such as alcohols. The investigation of the possible chemical reactions of different compounds in ISM could help to understand the formation and transport of molecules around the universe. In this thesis experiments were performed where pure methanol and etanol clusters as well as C60 clusters doped with those alcohols were formed upon pickup of individual molecules by superfluid He nanodroplets with an isothermic temperature of 0.37 K achieved by evaporative cooling of Helium (He) atoms. After pickup, the clusters were ionized by a 70 eV electron beam and then accelerated through a set of electrostatic lenses to a time-of-flight (TOF) analyzer, where the ion yield was recorded as a function of the mass to charge ratio. Molecular mechanics calculations with the MM2 force field as well as molecular dinamics simulations were performed to interpretate the spectra. Herein we report a chemical reaction occurring within the doped clusters upon ionization, where the alcohol molecules dehydrate forming water (H2O), dimethyl or diethyl ethers and also possibly ethene. There is evidence that the reaction is triggered by a proton coming from the fragmentation of one of the alcohol molecules due to the ionization process. The product ethers tend to leave the cluster after their formation while the H2O remains inside, solvated by alcohols. Magic numbers are also observed at the spectra for different number of C60 and alcohol molecules.
36
Roos, Matthias K. [Verfasser], and Regina de [Akademischer Betreuer] Vivie-Riedle. "Photoinitiated processes in functionally diverse organic molecules elucidated by theoretical methods / Matthias K. Roos ; Betreuer: Regina de Vivie-Riedle." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/117587812X/34.
Full text
37
Tasinato, Nicola <1981>. "Infrared Spectroscopy of Atmospherical and Astrophysical relevant Molecules: Spectral analysis, Line parameter retrievals and Study of collisional decay processes." Doctoral thesis, Università Ca' Foscari Venezia, 2010. http://hdl.handle.net/10579/71.
Full textAbstract:
This thesis encompasses different topics in the research field of IR spectroscopy, which includes line-by-line parameter and absorption cross sections retrievals, medium and high resolution analysis, and investigations about collisional processes. The research involving the line-by-line analysis has led to the development of a line-fitting software, VLSFP. Then, the line parameters of SO2 and H2C=CHF has been determined in the 8 – 9 mm atmospheric window by TDL spectroscopy. At medium resolution, the FT-IR spectrum of H2C=CHF has been investigated experimentally and through CCSD(T) ab-initio calculations. At high resolution, the spectrum of CF3Br, has been analysed in the 2v50 and v2 + v3 band regions. Absorption cross sections have been measured for SO2, H2C=CHF and CF3Br. Finally, the physics of the interactions of chirped IR laser radiation with low pressure gases, H2O, N2O and CO2, have been investigated by the frequency down-chirped radiation emitted by a QCL spectrometer employed in the intra-pulse method.
38
DJUIDJE, ERNESTINE NICAISE. "Design, Synthesis and Biological activities of Benzothiazole, Benzimidazole and Imidazopyrimidine polyphenols as multifunctional molecules against oxidative stress sustained processes." Doctoral thesis, Università degli studi di Ferrara, 2018. http://hdl.handle.net/11392/2488156.
Full textAbstract:
Reactive oxygen species regulate several essential physiological processes such as cell proliferation, differentiation, vascular tone and inflammation. However, their higher concentrations can have deleterious effects on many molecules including protein, lipid, RNA and DNA which leads to cell destruction causing several diseases including Parkinson’s diseases, inflammatory disease, cardiovascular, cancer, diabetes, Alzheimer’s disease, cataracts, autism and aging. Most of these diseases involve more physiopathological indications. Nevertheless, different pharmacological strategies, such as the use of multifunctional drugs, have been designed to prevent or restore redox imbalances and to treat complex diseases.
The present research project comes from the desire to synthesize multifunctional compounds with the capacity to present or treat multifactorial diseases such as cancer. For this purple, isosteric modification was performed on 2-Phenyl-1H-benzimidazol-5-sulfonic acid (PBSA) and three set of compounds were obtained: benzimidazole, benzothiazole and imidazopyrimidine derivatives. Synthesized compounds were evaluated for their UV-filter, antioxidant, antifungal and antiproliferative activites.
Photoprotective capacity was determined using spectrophotometric transmittance technique. DPPH and FRAP were performed to determine antioxidant activity. Diffusion method in Sabouraud Dextrose Agar (SDA) was used to evaluate anti-dermatophyte activity, while for broth microdilution method in RPMI was used to investigate anti-candida activity. Finally, MTS essay were performed to determine antioroliferative activity.
For benzimidazole derivatives, compound DE 35 was found to be a potential candidate in the development of multifunctional drugs, while for benzothiazole and imidazopyrimidine we respectively have 4g/4k and 14g. In addition, these set of compounds might have possible application as a drug for the treatment of neoplastic diseases such as childhood leukemia, pancreatic cancer and melanoma.Le specie reattive dell'ossigeno (ROS) regolano diversi processi fisiologici essenziali come la proliferazione cellulare, la differenziazione e il tono vascolare. Tuttavia, un'alta concentrazione di ROS può avere effetti indesiderati su molte molecole tra cui proteine, lipidi, RNA e DNA che portano alla distruzione cellulare causando varie pathologie ad esempio: malattie infiammatorie, malattie cardiovascolari, cancro, diabete, cataratta, autismo invecchiamento malattia di Parkinson e malattia Alzheimer. La maggior parte di queste malattie coinvolge più indicazioni fisiopatologiche. Diverse strategie farmacologiche, come l'uso di farmaci multifunzionali, sono state progettate per prevenire o ripristinare gli squilibri di riduzione dell'ossidazione e per trattare malattie complesse. Il presente progetto di ricerca nasce dal desiderio di sintetizzare composti multifunzionali con la capacità di prevenire o curare malattie multifattoriali come il cancro. Per questo motivo, le modifiche isosteriche sono state effettuate sull’ acido 2-fenil-1H-benzimidazol-5-solfonico (PBSA) e sono state ottenute tre serie di composti: derivati benzimidazolici, benzotiazolici e imidazopirimidici. I composti sintetizzati sono poi stati valutati per le loro attività UV filtrante, antiossidante, antifungina e antiproliferativa. La capacità fotoprotettiva è stata determinata utilizzando la tecnica di trasmittanza spettrofotometrica. DPPH e FRAP sono stati eseguiti per determinare l'attività antiossidante. Il metodo di diffusione in Sabouraud Dextrose Agar (SDA) è stato utilizzato per valutare l'attività anti-dermatofiti, mentre il metodo di microdiluizione del brodo RPMI è stato utilizzato per studiare l'attività anti-candida. Infine, è stato eseguito il saggio MTS per determinare l'attività anti-proliferativa. Per i derivati benzimidazolici, il composto DE 35 è risultato essere il potenziale candidato nello sviluppo di farmaci multifunzionali, mentre per i benzotiazolici e l'imidazopirimidici abbiamo rispettivamente 4g / 4k e 14g. Inoltre, questi set di composti potrebbero avere una possibile applicazione come farmaco per il trattamento di malattie neoplastiche come: la leucemia infantile, il cancro del pancreas e il melanoma.
39
Britton, Andrew James. "Charge transfer dynamics of adsorbate molecules on metal and semiconductor surfaces relating to fundamental processes in dye-sensitized solar cells." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13459/.
Full textAbstract:
The charge transfer dynamics between adsorbate molecules and surfaces are important for a variety of different technologies but especially for dye-sensitized solar cells. The main aim of this thesis was to study charge transfer between organic molecules and surfaces, especially relating to the situation observed in dye sensitized solar cells. This broad aim can be split into two distinct research objectives. One of these was to study the charge transfer between a Au (111) surface and a variety of different molecules using synchrotron-based photoemission spectroscopy. Resonant photoemission spectra of a C60 monolayer on Au (111) showed distinctive superspectator features which were not observed for the multilayer or clean gold spectra. These features were determined to be resultant from spectator decay involving electrons transferred from the gold substrate to the adsorbed molecule, either in the ground state or during the timescale of the core-hole lifetime. These features were also found for monolayers of bi-isonicotinic, isonicotinic, nicotinic and picolinic acid on gold, but not for the dye molecule, N3, on gold. This suggests that, although charge transfer occurs between the surface and the ligand molecules that constitute N3, no charge transfer occurs between the N3 dye molecule and the gold. The other objective was to determine whether the core-hole clock technique, previously only used in photoemission spectroscopy, could be adapted for resonant inelastic x-ray scattering. For this, bi-isonicotinic acid on TiO2 was studied because this system had already been explored using photoemission spectroscopy. The charge transfer times were measured using the relative decrease in the elastic peaks for the LUMO and LUMO+1 photon energies of the multilayer and monolayer. This gave a similar result to the photoemission studies providing more confidence for using this adaptation in situations where photoemission would be impossible, such as buried interfaces.
40
Kröner, Dominik (Dr rer nat ). "Analysis and control of light-induced processes in molecules: Electron and nuclear quantum dynamics for aspects of stereoisomerism and spectroscopy." Thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/7047/.
Full textAbstract:
The habilitation thesis covers theoretical investigations on light-induced processes in molecules. The study is focussed on changes of the molecular electronic structure and geometry, caused either by photoexcitation in the event of a spectroscopic analysis, or by a selective control with shaped laser pulses. The applied and developed methods are predominantly based on quantum chemistry as well as on electron and nuclear quantum dynamics, and in parts on molecular dynamics. The studied scientific problems deal with stereoisomerism and the question of how to either switch or distinguish chiral molecules using laser pulses, and with the essentials for the simulation of the spectroscopic response of biochromophores, in order to unravel their photophysics. The accomplished findings not only explain experimental results and extend existing approaches, but also contribute significantly to the basic understanding of the investigated light-driven molecular processes. The main achievements can be divided in three parts:
First, a quantum theory for an enantio- and diastereoselective or, in general, stereoselective laser pulse control was developed and successfully applied to influence the chirality of molecular switches. The proposed axially chiral molecules possess different numbers of "switchable" stable chiral conformations, with one particular switch featuring even a true achiral "off"-state which allows to enantioselectively "turn on" its chirality. Furthermore, surface mounted chiral molecular switches with several well-defined orientations were treated, where a newly devised highly flexible stochastic pulse optimization technique provides high stereoselectivity and efficiency at the same time, even for coupled chirality-changing degrees of freedom. Despite the model character of these studies, the proposed types of chiral molecular switches and, all the more, the developed basic concepts are generally applicable to design laser pulse controlled catalysts for asymmetric synthesis, or to achieve selective changes in the chirality of liquid crystals or in chiroptical nanodevices, implementable in information processing or as data storage.
Second, laser-driven electron wavepacket dynamics based on ab initio calculations, namely time-dependent configuration interaction, was extended by the explicit inclusion of magnetic field-magnetic dipole interactions for the simulation of the qualitative and quantitative distinction of enantiomers in mass spectrometry by means of circularly polarized ultrashort laser pulses. The developed approach not only allows to explain the origin of the experimentally observed influence of the pulse duration on the detected circular dichroism in the ion yield, but also to predict laser pulse parameters for an optimal distinction of enantiomers by ultrashort shaped laser pulses. Moreover, these investigations in combination with the previous ones provide a fundamental understanding of the relevance of electric and magnetic interactions between linearly or non-linearly polarized laser pulses and (pro-)chiral molecules for either control by enantioselective excitation or distinction by enantiospecific excitation.
Third, for selected light-sensitive biological systems of central importance, like e.g. antenna complexes of photosynthesis, simulations of processes which take place during and after photoexcitation of their chromophores were performed, in order to explain experimental (spectroscopic) findings as well as to understand the underlying photophysical and photochemical principles. In particular, aspects of normal mode mixing due to geometrical changes upon photoexcitation and their impact on (time-dependent) vibronic and resonance Raman spectra, as well as on intramolecular energy redistribution were addressed. In order to explain unresolved experimental findings, a simulation program for the calculation of vibronic and resonance Raman spectra, accounting for changes in both vibrational frequencies and normal modes, was created based on a time-dependent formalism. In addition, the influence of the biochemical environment on the electronic structure of the chromophores was studied by electrostatic interactions and mechanical embedding using hybrid quantum-classical methods. Environmental effects were found to be of importance, in particular, for the excitonic coupling of chromophores in light-harvesting complex II. Although the simulations for such highly complex systems are still restricted by various approximations, the improved approaches and obtained results have proven to be important contributions for a better understanding of light-induced processes in biosystems which also adds to efforts of their artificial reproduction.Die Habilitationsschrift behandelt theoretische Untersuchungen von durch Licht ausgelösten Prozessen in Molekülen. Der Schwerpunkt liegt dabei auf Veränderungen in der Elektronenstruktur und der Geometrie der Moleküle, die durch Bestrahlung mit Licht entweder bei einer spektroskopischen Untersuchung oder bei gezielter Kontrolle durch geformte Laserpulse herbeigeführt werden. Um die dabei auftretende Elektronen- und Kerndynamik zu simulieren, wurden vornehmlich quantentheoretische Methoden eingesetzt und weiterentwickelt. Die wissenschaftlichen Fragestellungen beschäftigen sich mit dem gezielten Verändern und dem Erkennen der räumlichen Struktur von Molekülen ohne Drehspiegelachse, der sog. molekularen Chiralität, sowie mit durch Licht eingeleiteten Prozessen in biologisch relevanten Pigmenten auf sehr kurzen Zeitskalen. Die entwickelten Ansätze und gewonnenen Erkenntnisse lassen sich drei Haupterfolge unterteilen: Erstens gelang die Entwicklung einer generellen Kontrolltheorie für das Ein- und Umschalten von molekularer Chiralität mit geformten Laserpulsen. Dabei wird die räumliche Struktur der vorgeschlagenen molekularen Schalter zwischen ihren stabilen sog. stereoisomeren Formen selektiv geändert, was sich auf ihre optischen und chemischen Eigenschaften auswirkt. Für komplexere Bedingungen, wie z.B. auf einer Oberfläche verankerten molekularen Schaltern verschiedener Orientierung, wurde eine neue Pulsoptimierungsmethode basierend auf Wahrscheinlichkeiten und Statistik entwickelt. Solche laserpulskontrollierten chiralen molekularen Schalter hofft man u.a. in der Nanotechnologie zum Einsatz zu bringen, wo sie z.B. als Informationsspeicher dienen könnten. Zweitens konnte geklärt werden, welche die wesentlichen Einflüsse sind, die das Erkennen von sog. Enantiomeren, das sind spiegelbildliche Moleküle von entgegengesetzter Chiralität, nach Ionisierung durch ultrakurze zirkular polarisierte Laserpulse ermöglichen. Diese Form des sog. Zirkulardichroismus in der Ionenausbeute erlaubt die quantitative und qualitative Unterscheidung von Enantiomeren in der Massenspektrometrie. Durch Simulation der Elektronendynamik während der Laseranregung konnte u.a. erstmals gezeigt werden, dass neben der Zirkularpolarisation der Laserpulse vor allem die schwachen magnetischen Wechselwirkungen für die Unterscheidung entscheidend sind. Drittens wurden die Spektren von in der Natur vorkommenden Pigmenten simuliert, welche u.a. an wichtigen biologischen Funktionen, wie dem Sammeln von Sonnenenergie für die Photosynthese, beteiligt sind. Die Lichtanregung führt dabei zu einer Veränderung der Elektronenstruktur und Geometrie der Pigmente, wobei letzteres wichtige Konsequenzen für die Verteilung der Energie auf die spektroskopisch beobachteten Molekülschwingungen mit sich bringen. Auch der wichtige Einfluss der biochemischen Umgebung auf die Elektronenstruktur der Pigmente bzw. den Energietransfer zwischen solchen wurde untersucht. Neben der Klärung experimenteller Ergebnisse ermöglichen die Untersuchungen neue Einblicke in die fundamentalen Prozesse kurz nach der Lichtanregung -- Erkenntnisse, die auch für die technische Nachahmung der biologischen Funktionen von Bedeutung sein können.
41
Scheffczyk, Jan David [Verfasser], André [Akademischer Betreuer] Bardow, Kai Akademischer Betreuer] Sundmacher, and Kai [Akademischer Betreuer] [Leonhard. "Integrated computer-aided design of molecules and processes using COSMO-RS / Jan David Scheffczyk ; André Bardow, Kai Sundmacher, Kai Olaf Leonhard." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1176421867/34.
Full text
42
Tarazkar, Maryam. "STRONG FIELD NONLINEAR OPTICS IN ATOMS AND POLYATOMIC MOLECULES: APPLICATION OF QUANTUM MECHANICAL METHODS TO PREDICT AND CONTROL LASER-INDUCED PROCESSES." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/364874.
Full textAbstract:
ChemistryPh.D.
The central objective of this dissertation is developing new methods for calculating higher-order nonlinear optical responses of atoms, molecules, and ions, and discussing the relevant physical mechanisms that give rise to harmonic generation, Kerr effect, and higher-order Kerr effect. The applications of nonlinear optical properties in development of predictive models for femtosecond laser filamentation dynamics, photoemission spectroscopy, imaging, and design of new molecular systems have motivated the theoretical investigations in advancing methods for calculating nonlinear optical properties and finding the optimum conditions for controlling the nonlinearities. The time-dependent nonlinear refractive index coefficient 4 n is investigated for argon and generalized for all noble gas atoms helium, neon, krypton, and xenon in the wavelengths ranging from 250 nm to 2000 nm, using ab initio methods. The secondorder polynomial fitting of DC-Kerr, electric-field-induced second-harmonic generation (ESHG), and static second-order hyperpolarizability have been performed, using an auxiliary electric field approach to obtain the corresponding fourth-order optical properties. An expression on the basis of static, DC-Kerr, DFWM fourth-order hyperpolarizability is derived, which allows the calculations of the DSWM coefficients with considerably reduced error. The results of the calculations suggest that filament stabilization is most likely to be induced by the generation of free electrons. Applications of these calculations resolve the HOKE controversy and are important for the development of predictive models for femtosecond laser filamentation dynamics. In a series of proof-of-concept studies, the approach was employed for calculating dynamic linear and nonlinear hyperpolarizability of the radical cations. In this regard, the polarizability and second-order hyperpolarizability of nitrogen radical cation were investigated, using density functional theory (DFT) and multi-configurational self-consistent field (MCSCF) methods. The open-shell electronic system of nitrogen radical cation provides negative second-order optical nonlinearity, suggesting that the hyperpolarizability coefficient for nitrogen radical cation, in the non-resonant regime is mainly composed of combinations of virtual one-photon transitions rather than two-photon transitions. The calculations of second-order optical properties for nitrogen radical cation as a function of bond length have been investigated to study the effect of internuclear bond distance on optical process. The variation of nonlinear responses versus bond length shows the potential application in finding optimum conditions for higher values of nonlinear coefficients. Furthermore, the computation of dynamic second-order hyperpolarizabilities for multiply ionized noble gases have been studied in the wavelength ranging from 100 nm to the red of the first multi-photon resonance all the way toward the static regime, using the MCSCF method. The results indicate that the second-order hyperpolarizability coefficients decrease when the electrons are removed from the systems. As the atoms reach higher ionization states, the second-order hyperpolarizability responses as a function of wavelength, become less dispersive. The second-order hyperpolarizability coefficients for each ionized species have also been investigated in terms of quantum state symmetries; the results suggest that the sign of the optical responses for each ionized atom depends on the spin of the quantum states defined for the ionized species. The calculations are of value for predictive models of high-harmonic generation in multiply ionized plasma at X-ray photon energies. This research also focuses on investigating possible mechanisms for photodissociation of polyatomic molecules (acetophenone and the substituted derivatives) ionized through strong field infrared laser pulses. In this regard, quantum mechanical methods are combined with pump-probe spectroscopy to understand and control the dissociation dynamics in strong field regime. The applications of quantum mechanical models in interpreting time-resolved wavepacket dynamics and achieving coherent control has stimulated the interest to explore the PESs and investigate the role of conical intersections in wavepacket dynamics in strong field regime. The electronic ground and excited states for acetophenone radical cation and the substituted derivatives have been investigated to probe the resonance features observed in measurements at 1370 nm with laser intensity of 1013 W cm-2. The ten lowest lying ionic potential energy surfaces (PESs) of the acetophenone radical cation were explored, and the three-state conical intersection was mapped onto the PES, using MCSCF model to propose a photo-dissociation mechanism for acetophenone undergoing tunnel ionization and elucidate the potential dissociation pathways for formation of benzoyl fragment ion, as well as phenyl, acylium, and butadienyl small fragment ions. Similar calculations are presented for propiophenone radical cation which support the existence of a one-photon transition from the ground ionic to a bright dissociative D2 state, where motion of the acetyl group from a planar to nonplanar structure within the pulse duration enables the otherwise forbidden transition. The wavepacket dynamics in acetophenone molecular ion is modeled using the classical wavepacket trajectory calculations, to propose the mechanism wherein the 790 nm probe pulse excites a wavepacket on the ground surface D0 to the excited D2 surface at a delay of 325 fs. The innovations of this research are used to design control strategies for selective bond-breaking in acetophenone radical cation, as well as design control schemes for other molecules.
Temple University--Theses
43
Brückner, Charlotte [Verfasser], and Bernd [Gutachter] Engels. "The Electronic Structure and Optoelectronic Processes at the Interfaces in Organic Solar Cells Composed of Small Organic Molecules - A Computational Analysis of Molecular, Intermolecular, and Aggregate Aspects / Charlotte Brückner ; Gutachter: Bernd Engels." Würzburg : Universität Würzburg, 2016. http://d-nb.info/1148944737/34.
Full text
44
Chang, Liang. "Sustainable Transformations of Methyl Coumalate : efficient Preparations of Unsaturated Carboxylic Acids, 2HPyrans, Trifluoromethyl Benzenes and Fluorescents Molecules." Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS109.
Full textAbstract:
Dans ce travail, nous décrivons le développement de nouvelles transformations utilisant le coumalate de méthyle, composé renouvelable biosourcé. Un couplage double séquentiel d'alkyl-alkyle ou d'alkyl-hydrure one-pot conduit à des acides insaturés d’intérêt. Nous décrivons une synthèse efficace de 2H-pyranes tétrasubstitués dans des conditions douces, puis nous décrivons une réaction efficace et sans solvant avec des dicétones trifluorométhylées, pour conduire à des benzènes trifluorométhylés. Enfin, nous avons rapporté une nouvelle stratégie générale de réaction de désaromatisation de composés hétérocycliques de type pyrido [1, 2-a] bicycliquesIn this work, we have described the development of new transformations using bio-based renewable methyl coumalate as feedstock. An iron and copper catalyzed one-pot sequential double alkyl-alkyl or alkyl-hydride 1,6-addition with methyl coumalate was described. We then described an efficient synthesis of tetrasubstituted 2H-pyrans under mild condition. Later we reported a solvent-free reaction of methyl coumalate with trifluoromethyl-β-diketones, in a tBuOK-catalyzed domino sequence. A novel reaction, for efficient C-C bond formation between the bio-based methyl coumalate and a variety of imines and aldehydes via MBH pathway was reported. Finally, we reported a novel, general dearomatization strategy with an unprecedented pyrido[1, 2-a] fused heterocyclic scope
45
Schaffer, Mario [Verfasser], Martin [Akademischer Betreuer] Sauter, Eckhard [Akademischer Betreuer] Worch, and Tobias [Akademischer Betreuer] Licha. "On the possibility of using organic molecules in the characterization of subsurface processes / Mario Schaffer. Gutachter: Martin Sauter ; Eckhard Worch ; Tobias Licha. Betreuer: Martin Sauter." Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044306920/34.
Full text
46
Hartmann, Gregor [Verfasser], Uwe [Akademischer Betreuer] Becker, Thomas [Akademischer Betreuer] Möller, and Jens [Akademischer Betreuer] Viefhaus. "Coherence effects of diatomic homonuclear molecules and sequential two-photon processes of noble gases in the photoionization / Gregor Hartmann. Gutachter: Thomas Möller ; Jens Viefhaus. Betreuer: Uwe Becker." Berlin : Technische Universität Berlin, 2014. http://d-nb.info/1065669879/34.
Full text
47
Villabona, Pedemonte Marc. "Photofunctional processes and materials based on molecular switches." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673837.
Full textAbstract:
Els interruptors moleculars han estat un camp de recerca important en els últims anys degut a la seva capacitat per interconvertir-se entre múltiples estats al estar exposats a un estímul (escriptura) i al fet de modificar les seves propietats després del canvi (lectura). Els interruptors moleculars que interaccionen amb llum per canviar d’estat o bé que modifiquen les seves propietats òptiques són d’especial interès ja que la llum permet un alt control espai temporal de forma no invasiva i la seva detecció té una alta sensibilitat. Per aquest motiu, durant aquesta tesis s’han desenvolupat múltiples materials i processos fotofuncionals els quals poden resumir-se en dues parts:
Per una banda, el caràcter multiestat d’una família de interruptors molecular (fluoro)cròmics basats en compostos espirocíclics zwitteriònics de Meisenheimer (SZMC), es va ampliar mitjançant la identificació d’un nou estat catiònic amb propietats òptiques distintives, el qual és pot generar tant electroquímicament com a través de l’adició d’un àcid. A més, es va investigar el comportament termo(fluoro)cròmic dels SZMC i es va demostrar que podien respondre tant a canvis en el dissolvent com a la presència d’anions. Aquest comportament multiestat i de resposta a múltiples estímuls va ser emprat en la preparació de una sèrie de materials fotofuncionals basats en SZMC com: un detector de pH d’ampli espectre, dispositius electro(fluoro)cròmics i sensors iònics, termals i de dissolvents.
Per altra banda, es van controlar tres processos químics amb ditieniletens (DTE) mitjançant llum. Primer, la introducció d’un grup electroacceptor EWG va permetre la modulació del pKa de fenols funcionalitzats amb DTEs. Després, el control amb dues longituds d’ona d’una reacció d’amidació es va aconseguir amb un estratègia similar a l’anterior utilitzant un éster activat basat en DTE. Aquest va reaccionar fins a 24 vegades més ràpid en el estat tancat generat amb llum UV (ie. activació amb UV) que amb l’estat obert obtingut sota irradiació amb llum visible (ie. desactivació amb visible). Finalment, la estratègia de controlar reaccions amb dos colors també va ser aplicada en la fotoligació mitjançant una reacció de oxo-Diels Alder d’un dienòfil basat en DTE actiu en la forma tancada (ie. Activacióamb llum UV, desactivació amb llum visible) i un diè generat en llum UV basat en orto-metilbenzaldèhid.Los interruptores moleculares han sido un campo de investigación importante en los últimos años debido a la capacidad de interconvertir-se entre múltiples estados al exponerse a un estímulo (escritura) y modificar sus propiedades (lectura). De especial interés han sido los interruptores moleculares que interaccionan con la luz ya sea para cambiar de estado o bien modificar sus propiedades ópticas en la transformación. Esto és debido a que la luz permite un alto control espaciotemporal al mismo tiempo que és no invasiva y altamente sensible a la detección. Por estos motivos, durante esta tesis se han desarrollados múltiples materiales y procesos fotofuncionales los cuales pueden resumirse en dos partes: Por un lado, el carácter multiestado de una familia de interruptores moleculares (fluoro)crómicos basados en compuestos espirocíclicos zwitteriònicos de Meisenheimer (SZMC) se amplió mediante la identificación de un nuevo estado catiónico, con propiedades ópticas distintivas, que se puede generar tanto electroquímicamente, como a través de la adición de ácido. Además, se investigó el comportamiento termo(fluoro)crómico de los SZMC y se demostró que podían responder tanto a cambios en el disolvente como a la presencia de iones. Este comportamiento multiestado i de respuesta a múltiples estímulos fue utilizado en la preparación de varios materiales fotofuncionales basados en SZMC como: un detector de pH de amplio espectro, dispositivos electro(fluoro)crómicos i sensores iónicos, termales i de disolventes. Por otro lado, se controlaron tres procesos químicos diferentes con interruptores moleculares fotoinducidos de tipo ditienileteno (DTE) mediante luz. Primero, la introducción de un grupo electroacceptor permitió la modulación del pKa de un fenol funcionalizado con un DTE. Segundo el control de una reacción de amidación con dos longitudes de onda fue conseguido con una estrategia similar a la anterior utilizando un ester activado basado en DTE. Este reacciona hasta 24 veces más rápido en el estado cerrado generado con luz ultravioleta (ie. activación con UV) que en el estado abierto que se obtiene al irradiar con luz visible (ie. desactivación con visible). Finalmente, el control de reacciones con dos colores de luz fue utilizado para controlar la reacción de oxo-Diels Alder entre un dienófilo basado en DTE activo en el estado cerrado (ie. activación con UV, desactivación con luz visible) i un dieno generado con luz UV basado en orto-metilbenzaldehido.
Molecular switches have been an important research field in the recent years due to its capacity to interconvert between multiple states through a stimulus (writing) and change their properties (reading). Of special interest are molecular switches that interact with light by either changing their optical properties or reacting as stimulus, due to its noninvasive high spatiotemporal control and sensitivity. As a result, several photofunctional materials and processes based on molecular switches were developed during this thesis which can be summarized in two topics. On the one hand, the multistate character of a family of (fluoro)chromic molecular switches based on spirocyclic zwitterionic Meisenheimer compounds (SZMC) was broadened by identifying a novel cationic state with distinctive optical properties, which could be achieved electrochemically or via acid addition. Moreover, the thermo(fluoro)chromic behavior of SZMCs was investigated and successfully demonstrated that they can respond to certain ions and solvents. This multistimuli-responsive and multistate character was then exploited for the preparation of a variety of photofunctional materials based on SZMCs: wide-range pH detectors, electro(fluoro)chromic displays, and thermal, ionic and solvent sensors. On the other hand, light controlled reactivity with dithienylethenes (DTE) was achieved for three chemical processes. First, the introduction of electrowithdrawing groups (EWG) allowed the modulation of the pKa in acetonitrile of a series of DTEs tethering phenol moieties. Second, a similar strategy allowed for the dual-color control of an amidation reaction employing DTE-based active esters which react up to 24 times faster in the UV-generated closed state (ie. activation with UV irradiation) than in the open state formed under visible illumination (ie depletion with visible light). Finally, two-wavelength control was also achieved for an oxo-Diels Alder reaction between a DTE-dienophile active in the closed state and a UV-generated diene based on orto-methylbenzaldehyde.
Universitat Autònoma de Barcelona. Programa de Doctorat en Química
48
Kröner, Dominik [Verfasser], and Peter [Akademischer Betreuer] Saalfrank. "Analysis and control of light-induced processes in molecules: Electron and nuclear quantum dynamics for aspects of stereoisomerism and spectroscopy / Dominik (Dr. rer. nat.) Kröner. Betreuer: Peter Saalfrank." Potsdam : Universitätsbibliothek der Universität Potsdam, 2014. http://d-nb.info/105113904X/34.
Full text
49
Buth, Christian. "Non-Hermitian perturbation theory for the electronic decay of excited and ionized molecules and identification of the electronic decay processes in the Auger decay of core-ionized Xenon-Fluorides." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10236341.
Full text
50
Öhrman, Olov. "Molecular sieve film catalysts." Licentiate thesis, Luleå, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26344.
Full textAbstract:
In this study, well defined ZSM-5 films were prepared on monoliths, ceramic foams, alumina beads, glass beads and crushed quartz glass by further refinement of a method originally developed at the division of Chemical Technology, Luleå University of Technology. The supports were seeded with silicalite-1 seeds and hydrothermally treated, either at 75 °C or at 150 °C in a single or several steps. By adding sodium to the solution the aluminum concentration increased in the zeolite, which is beneficial for catalytic activity. Consequently, films with different Si/Al ratios could be prepared. The film thickness could be controlled from 110 nm to 9000 nm. Short hydrothermal treatments and use of multi-step synthesis was utilized to prevent excessive bulk crystallization and ultrasound treatment was beneficial in order to remove sedimented crystals on top of the zeolite films. The choice of support material and its influence on the performance of thin ZSM-5 film catalysts was examined by testing the reactivity of the zeolite- coated materials in two reactions; para-xylene isomerization and triisopropylbenzene cracking. ZSM-5 films with a thickness of 150, 350, 800 and 2300 nm, respectively, were prepared on alumina beads and quartz glass. Based upon the zeolite content, the films on quartz glass were much more active for para-xylene isomerization and for cracking of triisopropylbenzene, which is attributed to poisoning of the films on alumina due to impurities in the support. Model parameters were fitted to experimental results. The simulations indicated that thicker films contained a higher fraction of defects, which may be caused by open grain boundaries and cracks. These defects explain higher xylene diffusivities and higher triisopropylbenzene cracking activity for thicker films. As expected, thicker films possessed higher diffusion resistance than thin films despite the higher fraction of defects. The present work has given substantial and valuable fundamental understanding of the performance of thin molecular sieve film catalysts. These findings will be beneficial for development of materials that may be used in novel industrial applications.Godkänd; 2003; 20070216 (ysko)