Dissertations / Theses on the topic 'Collision spectroscopy'
To see the other types of publications on this topic, follow the link: Collision spectroscopy.
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 'Collision spectroscopy.'
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
López, José G. "Theoretical studies of the dynamics and spectroscopy of weakly bound systems." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1127220592.
Full textAbstract:
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xv, 99 p.; also includes graphics (some col.). Includes bibliographical references (p. 95-99). Available online via OhioLINK's ETD Center
2
Lin, Yawei. "Spectroscopy of High Energy Ion-neutral Collisions." Thesis, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19720.
Full textAbstract:
This research work focused on studying the emission spectroscopy produced from the high energy ion-molecule collision processes in mass spectrometry. The collision experiments are described and divided into 4 chapters (Chapter 3, 4, 5, 6).N2O+● is an ion of atmospheric importance. In chapter 3 the investigation of the collision between high translational energy (4-8 keV range) N2O+● ions and Helium target gas in mass spectrometry using collision induced emission (CIE) spectroscopy is described.In chapter 4, the collision-induced emission (CIE) spectra from 4-8 keV collisions between projectile He+● ions and CO2 target gas (He+●/CO2) were obtained. In Chapter 5, to probe the validity of this hypothesis, CIE experiments were carried out to observe the photon emissions from keV collisions of a selection of projectile ions with O2 target gas. By studying the resulting CIE spectra, a second potential mechanism came to light, one that involves the nearly isoenergetic O2+. A → X state transition. In chapter 6, neutral hydroxymethylene and formaldehyde were generated by charge exchange neutralization of their respective ionic counterparts and then were reionized and detected as recovery signals in neutralization-reionization mass spectrometry in the modified VG-ZAB mass spectrometer.
3
Hu, Xiao-ming. "Angle resolved photoelectron spectroscopy study of small molecules." Thesis, University of Aberdeen, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277242.
Full textAbstract:
Under the title 'Angle Resolved Photoelectron Spectroscopy Study of Small Molecules', the thesis discussed the following aspects: Processes after the interaction of photons with atoms or molecules, including photoscattering, photoexcitation and fluorescence, photoabsorption, photodissociation and photoionization; Concepts of photoionization and photoelectron spectroscopy, including ionization potentials, photoionization cross sections, photoelectron angular distributions, shape resonances and autoionization; Theory of photoionization and photoelectron angular distributions, including central field approximation, Hartree-Fock calculations and multichannnel quantum defect theory; Apparatus for an angle resolved high resolution photoelectron experiment, including the synchrotron radiation source at Daresbury Laboratory, UK and an angle resolved electron spectrometer system from NIST/ANL, USA; The experiment on CO2 at Daresbury Laboratory, including electron spectrometer calibrations, experimental procedures and data processing; Results and discussion, including results for the photoionization cross sections of the CO+2X2 Πh state, vibrational branching ratios and asymmetry parameters for the synmmetric stretch vibrations (000) to (500) in the CO+2X2 Πh state in the photon wavelength region of 687 - 790AA with a resolution of about 0.1AA, analysis of photoelectron spectra taken at the Tanaka-Ogawa resonances and result for the Franck-Condon factors for transitions from the autoionizing states to different vibrational levels of the molecule.
4
Seamons, Scott Andrew. "The collision dynamics of OH(A)+H2." Thesis, University of Oxford, 2015. http://ora.ox.ac.uk/objects/uuid:36319557-1efa-4840-8f46-c15479945a0c.
Full textAbstract:
This thesis presents a joint experimental and theoretical study of a bimolecular collision between OH(A) and H2 diatoms. The study focuses on the relationship between the initial, j, and final rotational angular momentum, j'. This relationship is explored from both a scalar point of view by measuring rotational energy transfer (RET), and a vectorial viewpoint by considering the collisional depolarisation. The experimental technique used in this investigation, Zeeman quantum beat spectroscopy, is first demonstrated by applying it to the determination of the lab-frame orientation of OH(X) photofragments following the photolysis of H2O2. The H2O2 is photolysed by circularly-polarised light at 248 nm, and Zeeman quantum beat spectroscopy probes the angular momentum orientation as a function of the photofragment spin-rotation level. The results of this experiment are compared with orientation parameters predicted by a simulation that couples the rotation of the parent molecule to the torsional motion during bond cleavage. The calculations from the model agree qualitatively with those from the experiment. The Zeeman quantum beat spectroscopy technique is then used to monitor the evolution of angular momentum polarisation of OH(A) radicals during collisions with H2. The technique allows for the determination of depolarisation cross sections for oriented and aligned distributions, as a result of collisions with H2. Alongside this, cross sections for collisional quenching to non-reactive OH(X)+H2 and reactive H2O+H products are determined. By resolving the fuorescence with a monochromator the contributions to depolarisation from elastic collisions (the elastic depolarisation cross sections) are measured alongside cross sections for RET. Cross sections for total depolarisation and rotational energy transfer demonstrate only weak dependence on the rotational quantum number of the OH(A) radical, NOH. Competing quenching processes that fall with NOH are likely a considerable cause of this weak dependence. Furthermore, the polarisation of the angular momentum of OH(A) is randomised following RET. The elastic depolarisation cross sections make only a small contribution to the depolarisation and fall with increasing NOH. Collectively these trends have not been seen previously in similar studies on OH(A) collisions with atomic colliders. For the theoretical calculations, a four-atom quasi-classical trajectory (QCT) method has been developed, utilising Lagrangian multipliers to fix the OH(A) and H2 bonds. The calculations demonstrate that collisions involving the formation of complexes that survive for several rotational periods are prevalent in this collision system, and that these lead to large amounts of depolarisation. The calculations also demonstrate that RET in the H2 diatom supports higher levels of RET in OH(A) than seen in previous triatomic systems. Additionally, when one diatom is depolarised the accompanying diatom is typically also depolarised. These trends, at least in part, are owed to the highly attractive and anisotropic potential energy surface (PES) describing the interaction. The QCT calculations overestimate the experimentally-measured cross sections by more than a factor of 2. The calculations are adiabatic and do not account for the non-adiabatic activity associated with this collision system, and this is likely one cause of the discrepancies. In an attempt to further account for this overestimation, alternative angular momentum binning approaches for the QCT calculations are developed, but with limited success. Further exploration of the topology of the PES used in the calculations suggests that inadequacies in this surface are a major contributor to the discrepancies.
5
Noakes, Timothy Charles Quentin. "Coaxial impact collision ion scattering spectroscopy of semiconductor and metal surfaces." Thesis, University of Warwick, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308005.
Full text
6
Rock, Andrew Boyd, and n/a. "Low Energy Collision Induced Vibrational Relaxation in B3II+ou Iodine." Griffith University. School of Science, 1996. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050920.144408.
Full textAbstract:
Understanding energy transfer processes is an essential prerequisite for the deep understanding of all chemical processes. This thesis investigates the process of vibrational relaxation (or deexcitation) of highly vibrationally and electronically excited molecular iodine (I2) induced by very low energy collisions in a supersonic free jet with six foreign gases. In an investigation of the state-to-field relaxation of I2 (B 3II+ou, v = 16) induced by collisions with He at temperatures of 2 to 12 K we find that the absolute relaxation rates are an order of magnitude smaller than those at 300 K and that the explanation of the magnitudes of these rates does not require enhancement due to low energy orbiting resonances. We find that the rates scale well with estimated collision encounter rates that account for the attractive part of the intermolecular potential. A second investigation with a much wider scope explores vibrational relaxation from v = 21 to 24 with six foreign gases: He, Ne, Ar, H2, D2 and N2. For this investigation a new type of experimental procedure has been designed and implemented that records a detailed and complete map of the fluorescence from B3II+ouI2 that is resolved with respect to both fluorescence frequency and time. These not only yield state-to-field rates, but coupled with a novel deconvolution method for growth curve fitting, yield absolute state-to-state rates for vibrational relaxation processes with Av=-1, -2, -3 and -4. The dependence of the relaxation rates on the collision partner, temperature and Av are discussed. An exponential dependence on the vibrational energy gap may be adequate to characterise the Av dependence of vibrational relaxation. The frequency resolution of the experimental data also reveals that some of the energy released by vibrational de-excitation is transferred to the rotation of the I2 molecule. We find this process is best characterised by an exponential dependence on the change of I2 angular momentum and that its extent scales with the mass of the collision partner. Measurements of the low-energy collision-induced quenching of B 3II+ouI2 are also reported for all six foreign gases. The possibility arises from the rates that the mechanism for quenching by H2 and D2 at low temperatures is different to that of the other gases and to that for H2 and D2 at high temperatures.
7
Rock, Andrew Boyd. "Low Energy Collision Induced Vibrational Relaxation in B3II+ou Iodine." Thesis, Griffith University, 1996. http://hdl.handle.net/10072/366393.
Full textAbstract:
Understanding energy transfer processes is an essential prerequisite for the deep understanding of all chemical processes. This thesis investigates the process of vibrational relaxation (or deexcitation) of highly vibrationally and electronically excited molecular iodine (I2) induced by very low energy collisions in a supersonic free jet with six foreign gases. In an investigation of the state-to-field relaxation of I2 (B 3II+ou, v = 16) induced by collisions with He at temperatures of 2 to 12 K we find that the absolute relaxation rates are an order of magnitude smaller than those at 300 K and that the explanation of the magnitudes of these rates does not require enhancement due to low energy orbiting resonances. We find that the rates scale well with estimated collision encounter rates that account for the attractive part of the intermolecular potential. A second investigation with a much wider scope explores vibrational relaxation from v = 21 to 24 with six foreign gases: He, Ne, Ar, H2, D2 and N2. For this investigation a new type of experimental procedure has been designed and implemented that records a detailed and complete map of the fluorescence from B3II+ouI2 that is resolved with respect to both fluorescence frequency and time. These not only yield state-to-field rates, but coupled with a novel deconvolution method for growth curve fitting, yield absolute state-to-state rates for vibrational relaxation processes with Av=-1, -2, -3 and -4. The dependence of the relaxation rates on the collision partner, temperature and Av are discussed. An exponential dependence on the vibrational energy gap may be adequate to characterise the Av dependence of vibrational relaxation. The frequency resolution of the experimental data also reveals that some of the energy released by vibrational de-excitation is transferred to the rotation of the I2 molecule. We find this process is best characterised by an exponential dependence on the change of I2 angular momentum and that its extent scales with the mass of the collision partner. Measurements of the low-energy collision-induced quenching of B 3II+ouI2 are also reported for all six foreign gases. The possibility arises from the rates that the mechanism for quenching by H2 and D2 at low temperatures is different to that of the other gases and to that for H2 and D2 at high temperatures.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Science
Full Text
8
Watson, Cameron William. "A study of the spectroscopy and collision dynamics of SiX (X = F,C1) radicals." Thesis, University of Edinburgh, 1995. http://hdl.handle.net/1842/14646.
Full textAbstract:
This thesis concerns the study of state-specific collision-induced energy transfer processes between the SiF C2 Δ and B2Σ+ and the analogous SiC1 B'2 Σ+ states. Laser excitation spectra established the wavelengths at which the SiF B2Σ+ (v' = 0,1,2,4 and 5) and C2 Δ (v' = 0,1) levels could be populated selectively. The vibrational transition probabilities of the C - X and B - X systems were measured by observations of the resultant dispersed fluorescence. Comparison with the calculated Franck-Condon factors allowed an assessment of the behaviour of the transition dipole moment functions. The B - X transition moment was essentially invariant with internuclear separation. In contrast, the C - X transition moment was found to be strongly decreasing with increasing internuclear separation. These observations were justified on the basis of simple linear combination of atomic orbitals arguments. The radiative lifetimes of the C and B states were shown to be 94 ± 2 ns and ≤ 10 ns respectively by time resolved measurements of the C - X and B - X decays. Total quenching cross sections for removal of the SiF C (v' = 0,1) state were found to be large for the molecular quenchers H2, N2, CH4 and CO2, although no quenching was observed for Ar and He. A small but quencher dependent fraction of the removed C state molecules was transferred to the B2 Σ+ state except for CO2 as a quencher. The product B state vibrational populations were shown to correlate well with the Franck-Condon overlap between the initial and product vibronic states. The study of the isoelectronic SiC1 transfer system produced results in good agreement with, but of improved precision to those of previous studies. The B' state quenching was efficient for all collision partners with crosssections shown to correlate with long range attractive forces between the collision pair.
9
Verzhbitskiy, Ivan. "Spectroscopie de Raman de haute sensibilité dans des gaz à effet de serre : bandes de transitions doubles ou harmoniques." Angers, 2011. http://www.theses.fr/2011ANGE0076.
Full textAbstract:
Celle thése porte sur I'étude, grace a la diffusion Raman spontanée, de deux types de transitions qui apparaissent dans des gaz atmosphériques : les transitions simultanées et les transitions harmoniques. D’abord, l’effort a porté sur une double diffusion Raman incohérente dans Ie mélange SF6-N2, ou les deux molécules sont simultanément Ie siége d’une transition Raman autorisée. Un spectre trés précis a été enregistré et interprété quantiquement. Un bon accord entre théofie el expéfience a été trouvé pour les moments et les profits spectraux a condition que toutes les contributions importanles a tongue portée soient incorporées dans Ie modéle de polarisabilité induite par collisions. Les me‘canismes de polarisation présents dans Ie modéle simple de deux molécules polarisables ponctuelles élaienl suffisants pour décrire la composante anisolrope mais, pour rendre compte de la composante isotrope, l'utilisation du modéle bien plus sophistiqué "alome-molécule linéaire" a été nécessaire. Dans la deuxiéme partie de ce travail, la premiére harmonique de la vibration d'étirement asymetrique du CO2 a été étudiée. Contrairement aux précédentes qui sont induites par collision, celte transition est permise. La bande correspondanle s'avére presque entiérement dépolarisée, en accord avec l'affirmation §usqu'aIors vérifiée que pour la tfansition fondamentale) selon laquelle les vibrations asymétriques donnent lieu a des raies dépolarisées. Un prolocole rigoureux a été appliqué a l’interprétation des spectres enregislrés, impliquanl des effe/s anharmoniques et les couplages entre les modes. Nous avons simulé les profits en considérant les forts effets de couplages entre raiesThe purpose of this thesis was the understanding, viaspontaneous Raman scattering, of two types of transitions relevant to atmospheric gases: simultaneous transitions and overtone transitions. Regarding simultaneous transitions, the effort was mainly on double incoherent Raman scattering by SF6-N2, in which the two molecules simultaneously undergo a Raman-allowed transition. A highly accurate spectrum was recorded and interpreted quantum-mechanically. Agreement both in moments and in shapes was found with predictions made on the basis of a collision-induced polarizabilily model, provid€'d all Si9Sificant lo•9-ran9e contribul‹Ol0S were incorporated. The polarization mechanisms that survive in the simple model of two point-polarizable molecules were sufficient for the description of the anisotropic component, but, for the realistic description of the isotropic remnant, use of the far more sophisticated "atom-linear molecule" model was needed. In the second part of the thesis, the first overtone of the asymmetric stretch vibration, 2v3, of CO2 was studied. Unlike the previous transitions, which are collision-induced, overtones are allowed lransilions yet in the specific case of the 2v3 overtone the band was almost entirely depolarized, in agreement with the assertion (so far stated and checked for fundamental transition only) that asymmetrical vibrations give rise to depolarized lines. A rigorous protocol was applied to the interpretation of the reCOfded spectra, involving electric, optical and mechanical anharmonic effects and intermode couplings. Complete shape analysis was carried out from first principles to simulate the band profiles and the strong line-mixing effects
10
Dawson, Donald Frederick. "Collision-induced emission spectroscopy of small polyatomic molecules and tandem mass spectrometry of perfluorinated organics." Thesis, University of Ottawa (Canada), 2001. http://hdl.handle.net/10393/9035.
Full textAbstract:
The CIE studies presented in Chapter 2 consisted of a source generated fast moving 8 keV projectile-ion, M1+•, undergoing a collision encounter with a stationary target gas, G1, under single collision conditions (i.e., ≈90%T). During the collision event, a non-momentum transfer occurs, that deposits an amount of internal excitation energy, Delta(DeltaE int), into the projectile-ion, producing an excited electronic state (M1+•)* species. Thus the (M1 +•)* species may now exhibit optical emission and/or fragment into ground, M2+ + M3•, or excited, (M2)* + M3• M2+ + (M3•) *; (M2+)* + (M3•) *, electronic state dissociation products. Additionally, if the charge exchange process between M1+• and G1 is present, a ground M1, or excited (M1)* electronic state parent neutral may be produced. Thus, again the (M1)* species may now exhibit optical emissions and/or fragment into ground or excited electronic state dissociation products. As well, with respect to the stationary target gas the (G1)* and (G1+•)* species and/or their fragments may be produced. For the small polyatomic projectile-ions studied here of the N≡N+•, C≡O+•, O=C=O +•, O=C=C=O+• systems, intact parent-ion emissions were observed for all of them, except for the latter species. As well, intact parent neutral emissions were only observed for N≡N, C≡O. For the larger polyatomic projectile-ions studied here of the C6H6+•, C6F 6+•, and C4H4O+• systems, no intact-parent emissions were observed, only those of weak atomic and diatomic fragment emissions. The tandem mass spectrometry studies of perfluorinated organics, presented in Chapters 3 and 4, were conducted on a series of iodo, oxo and unsaturated compounds. In particular, the perfluoro iodo compounds were hoped (with iodine being such a good leaving group) to be possible ideal sources of unrearranged fragment perfluorocarbocations, CnF m+. However, unfortunately this did not always prove to be the case.(e.g., the primary metastable loss from (CF3) 3CI+• was unexpectedly FI and not I• ). For the perfluoro iodo compounds, the isomers of perfluorobutyl, C4F9I, and perfluoropropyl, C3F7I, iodides were utilized as precursors. (As well, (CF3)3C--C(CF 3)3 was utilized as a precursor for (CF3) 3C+). Specifically, it was proposed here that the (fragment) perfluorocarbocations, CnFm+ possessed a reserved cation stability order (i.e., primary > secondary > tertiary); CF 3CF2CF2CF2+ > (CF 3)3CFCF2+ > (CF3) 3C+; that is not seen in their respective hydrocarbon counterparts. (Abstract shortened by UMI.)
11
Killian, Thomas Charles 1969. "1S-2S spectroscopy of trapped hydrogen : the cold collision frequency shift and studies of BEC." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85260.
Full text
12
Conand, Clément. "Etude tectonique, pétrographique et géochimique de la zone de transition subduction-collision à Taïwan : rôle de l'héritage et de l'obliquité de la convergence." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30262.
Full textAbstract:
La chaîne de Taïwan est un exemple unique où il est possible d’étudier une transition subduction/collision active. L’obliquité de la convergence permet en effet d’observer du Sud vers le Nord les stades initiaux de l’accrétion continentale en mer jusqu’au stade mature de la collision. Je montre que la Chaîne Centrale au Sud de Taiwan, située la zone de transition, exhume des assemblages pétrographiques de grades croissants vers le Nord, dans un couloir décrochant senestre qui résulte du partitionnement de la convergence. Dans ce couloir l’extension sub-parallèle à la chaîne accommode une partie de l’exhumation. A proximité de la zone de suture principale, des assemblages de haute pression (12-15 kbars et 380-420 °C) associés à des blocs exotiques de serpentinites se sont mis en place dans un encaissant d’âge Miocène HT-BP associé à une intense déformation cisaillante senestre. Les analyses pétrologiques et géochimiques des mélanges ophiolitiques de Kenting et Lichi montrent que ces mélanges proviennent de deux sources situées à l’origine au pied de la marge continentale et dans la croûte océanique. Enfin, je propose, un nouveau modèle tectonique 3D du sud de Taïwan qui tient compte de l’architecture de la marge continentale, et qui met en avant la formation de la chaîne de Taiwan en contexte décrochantThe Taiwan collision is the unique example where to examine ongoing tectonic processes at the subduction/collision transition. The oblique convergence setting allows observations of first continental accretion offshore to the mature stage of collision onshore. I show that the southern Central Range, located at the transition, exhumed petrographic assemblages with peak metamorphism increasing northwards, in a corridor characterized by left-lateral transcurrent deformation. Extension sub-parallel to the belt is also understood as a major ingredient of rock exhumation. Near the suture zone, HP rocks (12-15 kbars and 380-420 °C) associated with isolated serpentinite bodies were emplaced in association with intense ductile strain localization in the strike-slip corridor. Petrographc and geochemical analyses of the Kenting and Lichi ophiolitic mélanges reveal that these mélanges originated from the distal rifted margin and the oceanic crust of the South China Sea. I propose a 3D geodynamic model of the evolution of the Taiwan orogen in which the rifted margin architecture is taken into account and the strike-slip kinematic component of the convergence is the main driver of mountain building
13
Gannouni, Mohamed Achref. "Approche théorique des collisions réactives de type ion-molécule." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1108/document.
Full textAbstract:
La collision entre l'ion hydroxyle (OH+) et l'atome d'hydrogène (H) joue un rôle majeur en physico-chimie de l'atmosphère et en astrophysique. Pour l'étude de ce système, nous avons générés la surface d'énergie potentielle tridimensionnelle (SEP-3D) globale doublet de la réaction H + OH+ --- H2O+ (X2B1)--- O + H2+. Les calculs électroniques ont été effectués au niveau MRCI avec la base aug-cc-pV5Z en incluant la correction des erreurs de superposition de base (BSSE). Cette SEP couvre la région moléculaire et les régions des longues portées pour les différents canaux : OH+ + H, O + H2+ et la réaction d'échange d'hydrogène. La qualité de la SEP a été validée après une comparaison des constantes spectroscopiques de H2O+ (X2B1) et des fragments diatomiques, des niveaux rovibroniques de H2O+ (X2B1), l'énergie de dissociation et de la barrière à linéarité pour H2O+ (X2B1) aux données expérimentales et théoriques existantes. Un bon accord est trouvé. Après avoir déterminé la SEP, nous avons utilisé les outils de la dynamique quantique indépendante du temps pour calculer les sections efficaces élastiques et inélastiques désexcitation de OH+ (v=0, j=1, 2, 3, 4, 5, 6 et 7) en collision avec l'atome d'hydrogène sur un large domaine d'énergie cinétique. Nous avons ainsi déterminé les taux désexcitation rotationnelle pour des températures allant de 10 à 200K. Nous avons également utilisé la surface quadruplet de Martinez et al. pour déduire ces taux désexcitation. Les résultats montrent que les sections efficaces inélastiques calculées sur la surface doublet sont en moyenne au moins deux à trois fois plus importantes que leurs correspondantes obtenues sur la surface quartet. Les potentiels à longue portée des deux surfaces étant identiques, ce résultat montre qu'un modèle basé sur la seule longue portée du potentiel ne pourrait pas rendre compte de la dynamique inélastique de ce systèmeThe collision between the hydroxyl cation (OH+) and hydrogen atoms (H) plays a major role in physical chemistry of the atmosphere and astrophysics. To study this system, we generated the global three-dimensional potential energy surface (3D-PES) of the reaction H + OH+ ---- H2O+ (X2B1) ---- O + H2+. The electronic calculations were performed at the MRCI level with aug-cc-pV5Z basis including the basis set superposition error (BSSE) correction. This PES covers the molecular region and the long ranges close to the OH+ + H, O + H2+ and the hydrogen exchange channels. The quality of the PES is checked after comparison of the spectroscopic constants of H2O+ (X2B1) and of the diatomic fragments, the rovibronic levels, the dissociation energy, and the barrier to linearity of H2O+ (X2B1) to available experimental and theoretical data. A good agreement is found. Then, we used the tools of time-independent Quantum Dynamics to calculate the elastic and inelastic cross sections for the de-excitation of OH+ in collision with the hydrogen atom over a wide range of kinetic energy. We have thus determined the rotational de-excitation rate coefficients for temperatures ranging from 10 up to 200K. The results show that the inelastic cross sections on the doublet surface are on average at least two to three times larger than their cross section obtained on the previously computed cross sections using the quartet surface. Since, the long range parts of the doublet and the quartet PESs are identical, our work invalidates hence previous cross section determination. When only long range potentials are considered. Therefore, we recommend using fully the global 3D PES for scattering and reactive collision relevant for atmospheric and astrophysical studies
14
Ngo, Ngoc Hoa. "Profil spectral des raies d’absorption de la vapeur d'eau pour l'étude de l'atmosphère de la terre par télédétection." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1134.
Full textAbstract:
Le travail présenté dans ce mémoire de thèse est consacré aux études théorique et expérimentale du profil spectral des raies d'absorption de la vapeur d'eau, une espèce clé dans l'atmosphère de la Terre. Le but de ce travail est de proposer une approche générale permettant de modéliser précisément la forme des raies d'absorption de H2O.La première partie de cette thèse porte sur la mesure des paramètres spectroscopiques de H2O pur et de H2O dans l'air dans l'infrarouge proche en utilisant un système de diode laser à cavité externe et la technique de spectroscopie d'absorption directe. Différents modèles de profil spectral existants sont utilisés pour ajuster les spectres mesurés. Les résultats montrent que le profil de Voigt habituel mène à de larges différences avec les spectres mesurés et qu'il est nécessaire de prendre en compte à la fois les changements de vitesse et les dépendances en vitesse des paramètres collisionnels pour décrire correctement le profil spectral. Dans la deuxième partie, une nouvelle modélisation du profil spectral de H2O est proposée. Le modèle développé est basé sur des résultats obtenus à partir de simulations de dynamique moléculaire et de calculs semi-classiques. Ce modèle tient compte à la fois des effets de changements de vitesse dus aux collisions et des dépendances en vitesse des paramètres collisionnels. En particulier, nous avons montré qu'il est important, pour H2O, de prendre en compte la corrélation entre les changements de la vitesse et ceux de l'état interne. Le modèle proposé est en très bon accord avec des spectres de H2O (H2O/H2O, H2O/N2 et H2O/Air) mesurés par différentes techniques et pour de larges gammes de pression et domaine spectral. En raison de sa complexité et de son temps de calcul élevé, l'utilisation du nouveau modèle est difficile dans des applications pratiques telles que les calculs de transfert radiatif. Dans la troisième partie, ce nouveau modèle est donc utilisé comme une référence afin de tester les différentes approches simplifiées existantes. Les résultats montrent que le modèle pCqSDHC (partially-Correlated quadratique-Speed-Dependent Hard-Collision) est le plus adapté pour modéliser le profil spectral des raies isolées de H2O, mais aussi d'autres systèmes moléculaire. Il permet en effet un très bon compromis entre la précision et l'efficacité demandée dans des applications pratiquesThis work is devoted to a theoretical and experimental study of the spectral shape of isolated transitions of water vapor, a key species of the Earth atmosphere. The purpose of these studies is to develop an accurate line-shape model taking into account different velocity effects affecting the spectral shape of H2O lines. In the first part of this thesis, spectroscopic line parameters of pure H2O and H2O diluted in air have been measured using an external cavity diode laser and a long-path absorption cell. Different existing line-shape models have been used to adjust the measurements. The results show that the widely-used Voigt profile leads to large differences with measured spectra and that it is necessary to take into account both the velocity changes and speed dependence effects to correctly model H2O line shapes. The second part of this work is devoted to the development of a new line-shape model, based on the results obtained from classical molecular dynamics simulations and semi-classical calculations. Both collision-induced velocity changes and speed dependence effects are taken into account by this model. Furthermore, we also show that the correlation between velocity changes and internal-state changes has to be accounted for to correctly describe H2O line shapes. Spectra of pure H2O, H2O in N2 and in air, calculated with the new model are in excellent agreement with those measured by different techniques and for large ranges of pressure and spectral domain. Its complexity and its large computational cost make the new model difficult to use for practical applications such as atmospheric radiative transfer. It is thus used, in the third part, as a “benchmark” in order to test different simplified line profiles and then to choose the proper one to fit measured spectra and to be used for atmospheric spectra prediction. The results show that the pCqSDHC (partially-Correlated quadratic-Speed-Dependent Hard-Collision) model is the most adapted to represent the line shape of H2O, but also of other molecules. This model offers a very good compromise between accuracy and computation efficiency and can be easily used in different practical applications
15
Graham, Lisa A. (Lisa Anne) Carleton University Dissertation Chemistry. "Studies in coincidence electron spectroscopy: finite collision volume effects and the characterization of an electron momentum spectrometer." Ottawa, 1991.
Find full text
16
López, José G. "Theoretical studies of the dynamics and spectroscopy of weakly bound systems." The Ohio State University, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=osu1127220592.
Full text
17
Hajsaleh, Jamal Y. (Jamal Yousef). "An Experimental Study of Collision Broadening of some Excited Rotational States of the Bending Vibration of Methyl Cyanide." Thesis, University of North Texas, 1993. https://digital.library.unt.edu/ark:/67531/metadc278369/.
Full textAbstract:
A double modulation microwave spectrometer is used to evaluate the linewidth parameters for some excited rotational components in the bending vibration v_8 of 13CH3 13C 15N and 13CH3C15N isotopomers of methyl cyanide. The linewidth parameters for self-broadening of the ΔJ=2←1 rotational components for the ground v_8 , 1v_8, and the 2v_8 vibrations were determined over a pressure range of 1 to 13 mtorr and at a temperature of 300 K. The double modulation technique is used to explore the high eighth derivative of the line shape profile of the spectral line. This technique proved to give good signal-to-noise ratios and enabled the recovery of weak signals. An experimental method is developed to correct for source modulation broadening. The tests of the ratios of the two inner peak's separation of the eighth derivative of the line showed that they were up to 95% similar to those for a Lorentzian line shape function. The line shapes were assumed to be Lorentzian for the theoretical analysis of the derivative profiles and comparisons were made between experiment and theory on this basis. Dipole moments for vibrationally excited states were calculated from linewidth parameters and show systematic decrease with the increase of excitation. Impact parameters were calculated using the "hard sphere" model of the kinetic theory of gases. The results were many times larger than the size of the molecule itself. This suggests that the dominant interaction is a long range dipole-dipole force interaction.
18
Holmes, Andrew J. "Studies of the spectroscopy and collision dynamics of some ion-pair states of I₂ using laser optical-optical double resonance excitation." Thesis, University of Edinburgh, 1989. http://hdl.handle.net/1842/15039.
Full text
19
Perkins, Thomas Edward James. "The effects of electronic quenching on the collision dynamics of OH(A) with Kr and Xe." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:5998e249-35ff-4d05-9c13-9b65d59b11d9.
Full textAbstract:
This thesis presents an experimental and theoretical study of the collision dynamics of OH(A2Σ+) with Kr and Xe. These two systems both exhibit a significant degree of electronically non-adiabatic behaviour, and a particular emphasis of the work presented here is to characterise the competition and interplay between electronic quenching on the one hand, and electronically adiabatic collisional processes on the other. Quenching takes place close to the bottom of the deepest potential well for both systems. In collisions that remain in the excited electronic state, this same region of the potential is also largely responsible for rotational energy transfer (RET) and the collisional depolarisation of angular momentum. Therefore, the direct competition between these processes suppresses the cross-sections for RET and collisional depolarisation from their expected value in the absence of quenching. To investigate this, experiments were carried out to measure cross-sections for the collisional transfer of electronic, vibrational and rotational energy in OH(A, v=0,1) + Kr and OH(A, v=0) + Xe. In addition, measurements were made of the j-j' correlation -- that is, the relationship between the angular momentum of the OH radical before and after a collision -- in collisions with Kr and Xe, using the experimental technique of Zeeman quantum beat spectroscopy. Collisions with both Kr and Xe tend to effectively depolarise the angular momentum of the OH radical, due to the very anisotropic character of the potential on which the process occurs. Electronic quenching, which plays an essential role in both systems, is more prevalent with xenon as the crossing to the ground state potential is located in a more accessible location. These experimental results were compared with single surface quasi-classical trajectory (QCT) calculations, where the overestimate of rotational energy transfer or collisional depolarisation helps to elucidate the degree to which the presence of quenching suppresses these processes. Surface hopping QCT was then used to account for non-adiabatic transitions in the theory, which led to an improvement in agreement with experiment. However, standard surface hopping QCT theory failed to account for the full extent of quenching in these two systems. A major focus of this work is therefore on the development of an extension to standard surface hopping QCT theory to incorporate rovibronic couplings. In non-linear configurations, the excited state of the OH + Kr, Xe systems has A' symmetry, while the ground state is split into symmetric (A') and antisymmetric (A'') components. For these symmetry reasons, coupling is restricted to the two states of the same symmetry, however a rotation of the correct (A'') symmetry can induce transitions to the A'' state too. Inclusion of all three electronic states, and the relevant couplings between them, is found to be crucial for a proper description of experimental reality.
20
Naylor, J. C. "The study of sputtering by concentration modulated absorption spectroscopy and the study of internal energy effects on collision induced decomposition mass spectrometry." Thesis, Swansea University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638299.
Full textAbstract:
The measurement of the absolute concentration of sputtered neutrals from a metal Li surface and polycrystalline NaC1 target has been achieved using the technique of concentration modulated absorption spectroscopy. The dependence of the amount sputtered on the target temperature, ion energy and target density has been investigated. The atomic density of the plume has been mapped in two dimensions under varying sputtering conditions. Utilising a previous theory describing a radial sputter distribution function the experiments have yielded values for the sputter yield of lithium and sodium. The profiling of sputtered neutrals across a planar glow discharge under varying cell conditions and discharge gases has been achieved using the laser spectroscopic technique. These experiments show that the sticking coefficient, α, of Li atoms on Li metal is non-unity. The experiments have been fitted using a Monte-Carlo model to generate values of α. An analytical model has also been developed to fit the experimental data. The model yields useful physical parameters concerning the plasma. This includes sticking coefficient data. The model has been compared with the computer-based method. High-energy collision induced decomposition mass spectrometry has been to investigate the possible effect of the internal energy of the precursor ion on the appearance of the spectra. Deuterated ethanol and the protonated deuterium counterpart were specifically produced in the ion source isomerically pure and to eliminate the presence of isotope scrambling. The experiments show that the spectra do vary significantly depending on the reaction conditions of temperature and pressure under which the protonated ethanol or the deuterated equivalent is produced.
21
Kumar, Vishant. "Fragmentation dynamics and geometrical arrangement of diatomic molecular clusters." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC245.
Full textAbstract:
L'analyse d'une expérience cinématiquement complète de collision ion-agrégats permet d'accéder à la dynamique de la dissociation des agrégats ionisés. Les cibles en phase gazeuse permettent d'étudier l'agrégat dans un environnement simple et de déterminer ses propriétés intrinsèques - en dehors de l'état condensé. De petits agrégats van der Waals de N2 et CO sont produits dans l'expansion supersonique d'un jet gazeux et irradiés par un faisceau d'ions multichargés de basse énergie produit par l'installation ARIBE/GANIL. Grâce à notre dispositif expérimental COLTRIMS (Cold Target Recoil Ion Momentum Spectroscopy), il est possible de mesurer en coïncidence les vecteurs d'impulsion 3D des fragments chargés résultant de la collision. Nous avons effectué une expérience pour étudier la dynamique de fragmentation et la géométrie des dimères et trimères de N2 et CO en utilisant un faisceau projectile Ar9+ à une énergie de 15 qkeV. Suite à une multiple capture électronique, la cible subit une dissociation en deux ou trois corps. Pour les voies à trois corps, deux processus distincts ont été identifiés dans lesquels les liaisons van der Waals et covalente se rompent simultanément ou séquentiellement. De plus, la technique d'imagerie par explosion coulombienne a été utilisée pour déterminer la structure tridimensionnelle des dimères moléculaires N2 et CO et des trimères. Nous avons observé que les molécules de N2 et CO sont orientés perpendiculairement à l'axe du dimer dans une configuration planaire (H) ou non-planaire (X) et que les trimères (N2)3 et (CO)3 présentent une géométrie en forme de triangle équilatéralThe analysis of a kinematically complete ion-cluster collision experiment provides insight in the dynamics of the ionized cluster dissociation. The gas phase targets allow to study the cluster in a simple environment and to determine their intrinsic properties for further condensed states. Small van der Waals clusters of N2 and CO are produced in the supersonic expansion of a gas jet and irradiated by a low energy highly charged ion beam produced by the ARIBE/GANIL facility. Using our experimental set-up COLTRIMS (COLd Target Recoil Ion Momentum Spectroscopy) it is made possible to measure in coincidence the 3-D momentum vectors of the charged fragments resulting from the collision. We have performed experiment to investigate the fragmentation dynamics and geometry of N2 and CO dimers and trimers using a projectile beam Ar9+ with the 15 qkeV energy. Following multiple electron capture, the target undergoes two or three body dissociation. For three body channels, two distinct processes have been identified in which the van der Waals and covalent bond breaks either simultaneously or sequentially. Additionally, the Coulomb explosion imaging technique has been used to determine the three dimensional structure of the N2 and CO molecular dimers and trimers. We found that the N2 and CO molecules sit perpendicularly to the dimer axis in a planar (H) or non-planar (X) configuration and that (N2)3 and (CO)3 trimers exhibit an equilateral triangular geometry
22
Springfield, James L. "Spectroscopy and Structure of Intermolecular Clusters and Rotational State-To-State Differential Cross-Sections for the HCI-X Collison System." Thesis, Griffith University, 2005. http://hdl.handle.net/10072/365402.
Full textAbstract:
One Colour-Resonant Two-Photon Ionisation, coupled with a supersonic expansion was used to study the rotationally cold excited electronic states of the water clusters of ortho-, meta- and para-difluorobenzene. Ground state rotational constants obtained through ab-initio calculations allowed rotational band contour simulations of these species to be performed, elucidating structural and spectroscopic features such as rotational band types, directions of transition dipole moments and excited state geometries. Confidence in the calculated ground state geometries, obtained through successful simulation of the rotational band contours, provided strength to the credibility of the vibrational frequencies acquired via these calculations. Analysis of ground state dispersed fluorescence spectroscopy utilising these ab-initio (geometry + frequency) optimisation calculations, allowed assignment of the ground state vibrational modes of each species. Furthermore, comparison of the assigned ground state modes with the excited state spectroscopy, affirmed assignment of the low frequency Van der Waals modes along with the higher frequency aromatic ring modes of these cluster species.
A novel technique that produces pseudo-selective excitation of ground state aromatic-rare gas cluster ions was used to assign the vibrational transitions of the D3[less than]D0 electronic excitation spectrum of para-Difluorobenzene+-Argonn=1,2. This technique works on the principle of providing varying degrees of excess energy to the ground state of the cluster ion, as well as altering the Franck-Condon factors for excitation to the D3 electronic state. Measurement of the redshifts for each pDFB-R (where R= Ar1, Ar2, Kr1, Kr2) cluster, revealed that the addition of a second rare-gas adatom doubled the redshift, and that Krypton ad-atoms produced a stronger redshift than argon as expected. It was also noted that the addition of a positive charge to the complex increased the redshift of the complexes, in accordance with our expectations. Rotational state-resolved differential cross sections (DCS's) for rotationally inelastic collisions of HCl with Ne, Ar, and Kr at ~545, ~538, and ~526 cm-1 of collision energy, respectively, were measured using velocity-mapped ion imaging. For each rotational state, the observed DCS's were found to be qualitatively similar. As collider mass was increased, the differential cross section became increasingly forward scattered. Calculations suggest that much of this difference is due to kinematic effects, but that the potential energy surface should be slightly more anisotropic for heavier colliders.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Science
Full Text
23
Bao, Zhuo. "Synchrotron Radiation Studies of Free and Adsorbed Molecules." Doctoral thesis, Uppsala University, Surface and Interface Science Division, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8610.
Full textAbstract:
This thesis contains two parts. The first part concerns the research work on free molecules using synchrotron-radiation-related techniques. Auger electron spectra of two free open-shell molecules, O2 and NO, were studied experimentally and theoretically. Photoionization experimental technique with tunable synchrotron radiation source was used to induce core-level electron ionization and obtain the KVV normal Auger electron spectra. A quantitative assignment of O2 normal Auger spectrum was obtained by applying ab initio CI calculations and LVI Auger line shape simulations including the bond length dependence of Auger transition rates. The photon energy dependence of normal Auger electron spectra was focused on with photon energies in the vicinities of core-ionization threshold energies. Consequently, the MAPCI (Molecular Auger Post Collision Interaction) theory was developed. Taking the near-threshold O2 normal Auger spectrum as an example, the two extreme cases of MAPCI effect, “atomic-like PCI” and “molecular PCI”, were discovered and discussed. The effect of shape resonance on near-threshold molecular normal Auger spectrum was discussed taking NO near threshold normal Auger spectra as example.
The second part deals with research work on the chemisorption of small epoxy organic molecules, ethylene oxide, methyl oxirane, on Si (100) surfaces. Synchrotron radiation related techniques, UPS, XPS and NEXAFS, were applied. Based on the valence photoemission spectra, C 1s and Si 2p XPS spectra, the epoxy ring opening reactions of these molecules in chemisorption process were proved. Further tentative search for the surface-adsorbate CDAD effect was performed, and no evident circular dichroism was confirmed.
24
Bull, James. "Application of Quantum Mechanics to Fundamental Interactions in Chemical Physics: Studies of Atom-Molecule and Ion-Molecule Interactions Under Single-Collision Conditions: Crossed Molecular Beams; Single-Crystal Mössbauer Spectroscopy: Microscopic Tensor Properties of ⁵⁷Fe Sites in Inorganic Ferrous High-Spin Compounds." Thesis, University of Canterbury. Department of Chemistry, 2010. http://hdl.handle.net/10092/4292.
Full textAbstract:
As part of this project and in preparation for future experimental studies of gas-phase ion-molecule reactions, extensive modification and characterization of the crossed molecular beam machine in the Department of Chemistry, University of Canterbury has been carried out. This instrument has been configured and some
preliminary testing completed to enable the future study of gas-phase ion-molecule collisions of H⁺₃ and Y⁻ (Y
= F, Cl, Br) with dipole-oriented CZ₃X (Z = H, F and X = F, Cl, Br). Theoretical calculations (ab initio
and density functional theory) are reported on previously experimentally characterized Na + CH₃NO₂, Na + CH₃NC, and K + CH₃NC systems, and several other systems of relevance. All gas-phase experimental and theoretical studies have the common theme of studying collision orientation dependence of reaction under singlecollision
conditions. Experimental measurements, theoretical simulations and calculations are also reported on some selected ferrous (Fe²⁺) high-spin (S=2) crystals, in an attempt to resolve microscopic contributions of two fundamental macroscopic tensor properties: the electric-field gradient (efg); and the mean square displacement (msd) in the case when more than one symmetry related site of low local point-group symmetry contributes to the same quadrupole doublet. These determinations have been made using the nuclear spectroscopic technique of Mössbauer spectroscopy, and complemented with X-ray crystallographic measurements.
25
Renoud, Julie. "Etude expérimentale des interactions du vent solaire avec la molécule prébiotique d'hydantoine (C3N2O2H4)." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30225.
Full textAbstract:
Cette thèse a pour objectif l'étude de l'interaction du vent solaire avec la molécule d'hydantoine C3N2O2H4, suspectée d'avoir joué un rôle dans l'apparition de la vie sur Terre. Cette molécule pré-biotique a été détectée dans les échantillons de plusieurs météorites et est donc potentiellement présente dans les éjectas gazeux des comètes, où elle interagit avec le vent solaire composé d'électrons et d'ions énergétiques. La physico-chimie de l'hydantoine en interaction avec des électrons de 100 eV qui sont l'un des composants majoritaires du vent solaire a été étudiée grâce au dispositif expérimental SWEET (Stellar Wind and Electrons interactions on astrophysical molecules - Experiment and Theory), développé au cours de cette thèse au LCAR (Laboratoire Collisions Agrégats Réactivité) dans l'équipe Interaction Ions Matière. Ce dispositif à faisceaux croisés pulsés permet la réalisation de collisions uniques entre une molécule neutre isolée et un électron ou un ion mono-chargé. Plusieurs spectrométries peuvent être réalisées en coïncidence pour une même interaction : spectrométrie des électrons émis et diffusés ainsi que spectrométrie ionique par imagerie des vecteurs vitesses (VMI) et par temps de vol. Ces techniques permettent d'identifier les fragments ioniques éventuellement formés, de caractériser la dynamique de fragmentation, de mesurer le seuil énergétique d'apparition des voies de dissociation et de sonder les états excités de la molécule. Afin d'étendre les études réalisées sur SWEET aux interactions de l'hydantoine avec les composants minoritaires du vent solaire (He2+ à 8 keV et O6+ à 30 keV), une campagne de mesures au GANIL (Grand Accélérateur National d'Ions Lourds, Caen, France) sur le dispositif COLIMACON a également été réalisée. Les résultats expérimentaux ont été complétés par des calculs de chimie quantique (DFT B3LYP/6-311++G(d,p)) donnant accès aux énergies et géométries de la molécule et de ses fragments pour divers états charge, ainsi qu'aux barrières de potentiel associées aux voies de fragmentation. Parmi les résultats importants obtenus, l'interaction de l'hydantoine avec le vent solaire a montré une faible résistance de la molécule à la charge (q>+3) et une ouverture de son cycle dans le dication qui pourrait être intéressante pour sa contribution potentielle à la formation de molécules plus complexes intervenant dans le vivant. Les seuils d'apparition des fragmentations majoritaires du cation et du dication ont également été mesurés pour la première fois et des schémas de réaction théoriques, en accord avec les mesures, ont été proposés. Les résultats nouveaux obtenus pendant cette thèse avec le dispositif SWEET ouvrent la voie à des mesures quantitatives des mécanismes de relaxation observés (sections efficaces absolues) qui permettront une caractérisation fine et complète de cette interaction spécifique : hydantoine - vent solaireThis thesis presents the study of the interaction of solar wind components with the hydantoin molecule C3N2O2H4, thought to have played a role in the appearance of life on Earth. This prebiotic molecule was detected in several meteorite samples and is thus potentially present in cometary outgasing, where it interacs with solar wind composed of electrons and energetic ions. The physico-chemistry of hydantoin in interaction with 100 eV electrons, which are one of the major components of solar wind, was studied with the new experimental apparatus SWEET (Stellar Wind and Electrons interactions on astrophysical molecules - Experiment and Theory), which was set-up during this thesis in the LCAR (Laboratoire Collisions Agrégats Réactivité), within the Ion Matter Interaction team. This is a crossed-beam apparatus which enables the investigation of unique collisions between one neutral isolated molecule and one electron or ion. The coincident use of several spectrometries techniques (spectrometry of emitted and scattered electrons and ionic spectrometry by velocity map imaging and time of flight) enables the identification of ionic produced fragments, the characterisation of the fragmentation dynamics, the measurement of the energetic threshold for dissociation pathways, and the probe of molecular excited states. The results obtained on SWEET were extended to the study of the interaction of hydantoin with multi-charged minority ions of solar wind (He2+ at 8 keV and O6+ at 30 keV), studied during a measurement campaign on the COLIMACON set-up at the GANIL (Grand Accélérateur National d'Ions Lourds, Caen, France). Experimental results were completed by a quantum chemistry approach (DFT B3LYP/6-311++G(d,p)) to calculate the energy and geometry of the molecular systems as well as the dissociation potential barriers. As important results, the interaction between hydantoin and the solar wind components shows that the molecule easily fragments when multiply charged (q>+3) and the cycle opens when doubly charged, implying a high reactivity interesting within the framework of early Earth chemistry. The energetic thresholds for the major cation and dication fragmentations were measured and a theoretical reaction scheme was proposed, in accordance with the experimental measurments. The first results of the SWEET apparatus pave the way to quantitative measurements such as the absolute cross section of the observed relaxation processes, to complete the characterisation of the specific hydantoin - solar wind interaction
26
Davies, Julia Ann. "Electron spectroscopy of selected atmospheric molecules and hydrocarbons." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283221.
Full text
27
Wilson, Emma. "Gamma spectroscopy of 207Tl126 populated in deep-inelastic collisions." Thesis, University of Surrey, 2015. http://epubs.surrey.ac.uk/807041/.
Full text
28
Chaudhry, M. A. "Electron and X-ray spectroscopy of electron-atom collisions." Thesis, University of Stirling, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379507.
Full text
29
Bell, Ian Mac. "Alignment production by atomic collisions in a laser field." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240609.
Full text
30
Astill, A. G. "Spectroscopic and collision dynamic studies of Na2̲ and I2̲." Thesis, University of Sussex, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383502.
Full text
31
Thi, Ngoc Ha Tran. "Diagnostics par spectroscopies femtosecondes des caractéristiques physiques d'un milieu en combustion." Besançon, 2004. http://www.theses.fr/2004BESA2006.
Full text
32
Baumgartner, Sean. "COLLISIONAL DEPOLARIZATION OF THE ATOMIC SODIUM 3S2S1/2 → 3P2P3/2 → 5S2S1/2 TRANSITION WITH ARGON AND XENON BUFFER GAS BY SPECTRAL HOLE-BURNING." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1311956327.
Full text
33
Hedley, John. "Collisional and radiative processes in atomic spectra." Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295500.
Full text
34
Labiad, Hamza. "Transfert d'énergie rotationnelle lors des collisions de CO-Ar et CO-H₂ à très basses températures pour des applications astrophysiques." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S147/document.
Full textAbstract:
Cette thèse a été effectuée au sein de l’Institut de Physique de Rennes, et qui porte sur le transfert d’énergie rotationnelle lors des collisions de CO-Ar et CO-H2 à très basses températures pour des applications astrophysiques. Comprendre la constitution du milieu interstellaire (MIS), son évolution et ses propriétés physiques telles que la température et la densité, nécessite la connaissance de l’efficacité des collisions atomiques et moléculaires. Cette thèse expérimentale a été motivée par cet objectif. Le MIS et plus particulièrement les nuages moléculaires froids sont caractérisés par des températures très basses atteignant ~ -260 °C. Afin de reproduire ces conditions, on a utilisé la technique CRESU (Cinétique des Réactions en Ecoulement Supersonique Uniforme). Deux systèmes de collisions ont été étudiés : CO-Ar et CO-H2 pour leur impact dans les modèles astrophysiques (dits aussi modèles de transfert radiatifs). Une technique spectroscopique IR-VUV (Infrarouge-Ultraviolet dans le vide) en double résonance à base de lasers pulsés a été utilisée pour la détection et le diagnostic de l’efficacité des collisions et la détermination les constantes de collisions. Les résultats expérimentaux obtenus (pour la première fois) ont été comparés à des prédictions basées sur des calculs théoriques très avancés de mécanique quantique. Un très bon accord a été obtenu, ce qui a permis de tester et valider ces calculs théoriques d’un côté, et aussi de pouvoir fournir des constantes de collisions robustes qui vont être utilisées par les astrophysiciens pour modéliser et déterminer les propriétés physiques du MIS, ainsi qu’interpréter les spectres astrophysiques obtenus par des télescopes ou des satellitesIn the quest to understand the universe, astrophysicists observe and make models for astrophysical objects in the sky. The interstellar medium, ISM, in particular is of central importance since it represents the matter that exists in the space between stars in a galaxy, and in which stars and planets form. Understanding it, its constituents and its evolution and characteristics requires the quantification of several chemical and physical processes, including collision processes. In this work, we used the CRESU technique to reproduce very cold environments of astrophysical media, in particular dense molecular clouds in the ISM. We studied experimentally rotational energy transfer, RET, resulting from inelastic collisions at very low temperatures using a pump-probe laser-based spectroscopic technique for the purpose of measuring constants quantifying collisions. Two types of constants were determined: the first are total removal constants of RET resulting from a specific rotational quantum state to all possible final rotational quantum states, and the second are more detailed information consisting in rate constants from a specific rotational quantum state to another specific rotational quantum state, so-called state-to-state rate constants. Two experiments have been performed involving Carbone monoxide molecule, CO, as a target molecule of collisions. The first involves argon, Ar, as a projectile atom, and the second molecular hydrogen, H2, as a projectile molecule. Both collisional systems play an important role in a wide range of areas including gas-phase phenomena and astrophysical applications. In the first experiment, we investigated collisions between CO and Ar, from 293 K down to 30 K. IR-VUV double resonance technique has been exploited to measure, directly for the first time, absolute values of total removal and state-to-state constants of collisions. The experimental results have been compared to theoretical predictions based on a diatom-atom model of collision, where very good agreement was observed. In the second experiment, we investigated collisions between CO and H2 (the most abundant molecules in the ISM) from 293 K down to 5.5 K focusing on the very low temperatures of dense molecular clouds in the ISM. For the first time, total removal and state-to-state constants have been measured and compared to theoretical predictions of a highly accurate diatom-diatom model of collisions, where excellent agreement was observed. The results obtained in this thesis served to validate theoretical models of molecular collisions, helping the continuous efforts for pushing the frontiers of theoretical models. In the astrophysical side, the obtained collisional constants will be taken into account in modeling of many astrophysical media
35
Ezzeddine, Rana. "Le rôle des collisions avec l'hydrogène dans la determination hors-ETL de l'abondance du fer dans les étoiles froides." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS147/document.
Full textAbstract:
La détermination d'abondances stellaires très précises a toujours été et reste un point clé de toute analyse spectroscopique.Cependant, de nombreuses études ont montré que l'hypothèse de l'équilibre thermodynamique local (ETL), largement utilisée dans les analyses spectroscopiques est inadéquate pour déterminer les abondances et les paramètres stellaires des étoiles géantes et pauvres en métaux où les effets hors-ETL dominent. C'est pourquoi, une modélisation hors-ETL des spectres stellaires est cruciale afin de reproduire les observations et ainsi déterminer avec précision les paramètres stellaires.Cette modélisation hors-ETL nécessite l'utilisation d'un grand jeu de données atomiques, qui ne sont pas toujours connues avec certitude. Dans les étoiles froides, les taux de collisions de l'atome d'hydrogène sont une des principales sources d'incertitudes. Ces taux sont souvent calculés en considérant une approche classique (l'approximation de Drawin) pour les transitions permises lié-lié et les transitions d'ionisations. Cette approche classique tend à surestimer les taux de collisions et ne reproduit pas correctement le comportement avec les énergies.Dans cette thèse, nous démontrons que l'approximation de Drawin ne peut pas décrire les taux de collisions dans le cas de l'atome d'hydrogène. Nous présentons une nouvelle méthode pour estimer ces taux, par le biais d'ajustement sur des taux quantiques existant pour d'autres éléments.Nous montrons que cette méthode d'ajustement quantique (MAQ) est satisfaisante pour les modélisations hors-ETL lorsque les taux quantiques dédiés ne sont pas effectivement disponibles.Nous testons cette nouvelle méthode, avec le modèle d'atome de Fer que nous avons développé, sur des étoiles de référence issues « du Gaia-ESO survey ».En partant de paramètres photosphériques non-spectroscopiques connus, nous déterminons les abondances (1D) en fer de ces étoiles de référence dans les cas ETL et hors-ETL .Nos résultats dans le cas hors ETL conduisent à un excellent accord entre les abondances de FeI et FeII avec de faibles écarts types de raies à raies, particulièrement dans le cas des étoiles pauvres en métaux.Notre méthode est validée par comparaison avec de nouveaux calculs quantiques préliminaires sur l'atome de Fe I et d'hydrogène, dont les ajustements sont en excellent accord avec les nôtresDetermination of high precision abundances has and will always be an important goal of all spectroscopic studies. The use of LTE assumption in spectroscopic analyses has been extensively shown in the literature to badly affect the determined abundances and stellar parameters, especially in metal-poor and giant stars which can be subject to large non-LTE effects. Non-LTE modeling of stellar spectra is therefore essential to accurately reproduce the observations and derive stellar abundances. Non-LTE calculations require the inputof a bulk of atomic data, which may be subject to uncertainties. In cool stars, hydrogen collisional rates are a major source of uncertainty, which are often approximated using a classical recipe (the Drawin approximation) for allowed bound-bound, and ionization transitions only. This approximation has been shown to overestimate the collisional rates, and does not reproduce the correct behavior with energies. We demonstrate in this dissertation the inability of the Drawin approximation to describe the hydrogen collisional rates.We introduce a new method to estimate these rates based on fitting the existing quantum rates of other elements. We show that this quantum fitting method (QFM) performs well in non-LTE calculations when detailed quantum rates are not available. We test the newly proposed method, with a complete iron model atom that we developed, on a reference set of stars from the Gaia-ESO survey. Starting from well determined non-spectroscopic atmospheric parameters, we determine 1D, non-LTE, and LTE iron abundances for this set ofstars. Our non-LTE results show excellent agreement between Fe I and Fe II abundances and small line-by-line dispersions, especially for the metal-poor stars. Our method is validated upon comparison with new preliminary Fe I+H quantum calculations, whose fits show an excellent agreement with ours
36
Hodgkinson, Jacqueline. "Study of slow multiply charged ion-atom collisions using translational energy spectroscopy." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318774.
Full text
37
Collins, Timothy L. D. "Inelastic rotational transfer differential cross-sections for Li2-rare gas collisions." Thesis, University of Sussex, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282082.
Full text
38
Mosely, Jacqueline Anne. "Collisional activation and target capture with massive ions by means of magnetic-sector mass spectroscopy." Thesis, University of Warwick, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263606.
Full text
39
Hultquist, Adam. "Collisional broadening by hydrogenfor stellar spectroscopy : extension towards high-lying states." Thesis, Uppsala universitet, Teoretisk astrofysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-389326.
Full textAbstract:
The object of this thesis is to extend the current tables for two useful quantities when calculatingcollisional broadening, the cross-section of interaction and the velocity parameter.These quantities, which have hitherto been tabulated for lower states, have now been calculatedfor higher lying states and are used in the ABO - model for spectral line broadening.Having larger tables for these values enables broadening calculations for more spectral linesand this thesis shows examples of calculations which beneted from this. During the calculationsof the tables some unexpected behaviour in the distribution of values arose whichhas not been seen previously. This could point to an unknown underlying mechanism.
40
Lu, Jessica Weidgin. "Dynamics of Atmospherically Important Triatomics in Collisions with Model Organic Surfaces." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/77045.
Full textAbstract:
Detailed investigations of molecular collisions at the gas-surface interface provide insight into the dynamics and mechanisms of important interfacial reactions. A thorough understanding of the fundamental interactions between a gas and surface is crucial to the study of heterogeneous chemistry of atmospheric organic aerosols. In addition to changing the chemical and physical properties of the particle, reactions with oxidizing gases may alter aerosol optical properties, with implications for the regional radiation budget and climate. Molecular beams of CO₂, NO₂ and O₃ were scattered from long-chain methyl (CH₃-), hydroxyl (OH-), vinyl (H₂C=CH-) and perfluorinated (CF₃(CF₂)₈-, or F-) ω-functionalized alkanethiol self-assembled monolayers (SAMs) on gold, to explore the reaction dynamics of atmospherically important triatomics on proxies for organic aerosols. Energy exchange and thermal accommodation during the gas-surface collision, the first step of most interfacial reactions, was probed by time-of-flight techniques. The final energy distribution of the scattered molecules was measured under specular scattering conditions (θi = θf = 30°). Overall, extent of energy transfer and accommodation was found to depend on the terminal functional group of the SAM, incident energy of the triatomics, and gas-surface intermolecular forces. Reaction dynamics studies of O3 scattering from H2C=CH-SAMs revealed that oxidation of the double bond depend significantly on O₃ translational energy. Our results indicate that the room-temperature reaction follows the Langmuir-Hinshelwood mechanism, requiring accommodation prior to reaction. The measurements also show that the dynamics transition to a direct reaction for higher translational energies. Possible environmental impacts of heterogeneous reactions were probed by evaluating the change in the optical properties of laboratory-generated benzo[a]pyrene (BaP)-coated aerosols, after exposure to NO₃ and NO₂, at 532 nm and 355 nm by three aerosol analysis techniques: cavity ring-down aerosol spectroscopy (CRD-AS) at 355 nm and 532 nm, photoacoustic spectroscopy (PAS) at 532 nm, and an aerosol mass spectrometer (AMS). Heterogeneous reactions may lead to the nitration of organic-coated aerosols, which may account for atmospheric absorbance over urban areas. Developing a detailed understanding of heterogeneous reactions on atmospheric organic aerosols will help researchers to predict the fate, lifetime, and environmental impact of atmospherically important triatomics and the particles with which they collide.Ph. D.
41
Wood, Mark. "Combined radiative and collisional effects in the spectrum of ytterbium." Thesis, University of Newcastle Upon Tyne, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295510.
Full text
42
Asplet, William. "Etude des interactions entre les défauts lacunaires et les solutés Y,O, Ti pour mieux comprendre leur rôle dans la formation des nanoparticules d'oxydes dans les aciers ODS." Thesis, Orléans, 2018. http://www.theses.fr/2018ORLE2056/document.
Full textAbstract:
Cette thèse est dédiée à l’étude des interactions entre les défauts lacunaires et les solutés (Y, Ti, O) pour mieux comprendre la formation des nanoparticules d’oxyde dans les aciers ODS (Oxide Dispersion Strengthened). Ces aciers sont envisagés comme matériau de structure dans la prochaine génération de réacteurs nucléaires fission et fusion. Leurs bonnes propriétés reposent essentiellement sur une répartition homogène de nanoparticules (YxTiyOz) de très faible taille. Cependant, l’obtention de cette répartition n’est pas encore maitrisée et le mécanisme de formation de ces nanoparticules n’est pas encore bien défini. Des modèles théoriques montrent que la présence de lacunes pendant l’étape de broyage pourrait impacter la formation de ces nanoparticules. Cette étude fait suite à la thèse de C. He et apporte de nouveaux résultats et de nouvelles interprétations et conclusions. Des implantations avec des ions Y, Ti, O ont été réalisées afin de simuler l’étape de broyage de ces aciers ODS. Elles ont permis d’introduire des défauts et les solutés désirés dans la matrice de fer α. Nous avons ensuite étudié les interactions entre les solutés et les défauts générés dans la matrice. La nature des défauts induits a été étudiée en fonction de l’ion implanté et de traitements thermiques après implantation par spectroscopie d’annihilation de positons (PAS) et corrélée avec les profils en profondeur des solutés obtenus par spectrométrie de masse des ions secondaires (SIMS). Les caractéristiques d’annihilation de certains défauts encore inconnues ont pu être déterminées. Les mesures SIMS ont montré que le titane ne migre pas entre 100 et 450°C et que l’oxygène présente un comportement complexe de migration et de piégeage dépendant de la température et de la microstructure des matériaux. Les résultats PAS montrent que les implantations ioniques conduisent à la formation de clusters lacunaires, de complexes lacunes-solutés et de dislocations dont la proportion change en fonction de la profondeur et de la nature de l’ion implanté. Les clusters de lacunes Vn et les dislocations sont détectés au-delà du pic d’implantation avec une fraction plus importante pour les dislocations indiquant que les défauts ont pu migrer pendant l’implantation. La proportion des complexes lacunes-solutés est maximale dans la zone d’arrêt des ions. Elle est en accord avec les énergies de liaison théoriques des complexes lacunes-soluté. La nature et la distribution des défauts formés évoluent en fonction de la température de recuit. Les clusters lacunaires Vn disparaissent entre RT et 300°C alors que les dislocations sont éliminées à partir de 400°C. Des phases oxydes sont détectées pour des recuits à 500 et 550°C en lien avec la contamination en oxygène. Des défauts dont la nature est non identifiée ont été mis en évidence pour des recuits réalisés entre 300 et 400°C dans les implantations O, Y et Y+OThis PhD thesis is dedicated to the study of interaction between vacancies and Y, Ti,O solutes for a better understanding of formation of oxide nanoparticles in ODS steel (Oxide Dispersion Strengthened). These ODS steels are considered as structural material for the next generation of fission and fusion nuclear reactors. Their good properties are induced by the fine dispersion of low size oxide nanoparticles. However, obtaining this distribution is not mastered and atomic scale clustering is not yet defined. Furthermore, it was shown by theoretical models that the presence of vacancy during mechanical alloying could affect the formation of these nanoparticles. This study follows upon on a previous study made by C.He, and bring new results, new interpretation and conclusions. Some implantations with Y, Ti, O ions with several energy have been made in order to simulate the mechanical alloying step used for ODS steel fabrication. Theses irradiations have induced defects and solutes into the iron matrix. Then we characterized samples using positron annihilation spectroscopy (PAS) and secondary ion mass spectrometry (SIMS). The nature of defects was studied according to nature of the implanted ion and the annealing temperature by PAS and correlated to depth profiles of solutes obtained by SIMS. Annihilation characteristics of some defects still unknown were able to be determined thanks to positron lifetime measurements. SIMS analysis showed that titanium doesn’t migrate for annealing experiments between 100°C and 450°C and that oxygen show a complex behavior of migration and trapping dependent on the microstructure of the material. PAS results show that ionic implantations produce vacancy clusters, dislocations and solutes-vacancies complex. Their proportion changes as a function of depth and nature of these irradiations. Vacancy clusters and dislocations are detected deeper than the implantation peak with a higher fraction for the dislocations indicating that the defects were able to migrate during implantations. The fraction of vacancy-solutes complexes is the highest in the ion stopping zone and is in a good agreement with the theoretical binding energy of vacancies-solutes complex. The nature and the distribution of the defects evolve according to the annealing temperature. Vacancy clusters disappear between RT and 300°C while the dislocations are eliminated from 400°C. Oxide phases are detected for annealing at 500 and 550°C in relation with the oxygen contamination during these annealings. Some defects which the nature is not yet identified were highlighted for annealing between 300 and 400°C for Y, O and Y+O irradiations
43
Yamaguchi, Atsushi. "Metastable State of Ultracold and Quantum Degenerate Ytterbium Atoms: High-Resolution Spectroscopy and Cold Collisions." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/124352.
Full text
44
Alagappan, Azhagammai. "Studies of collisional energy transfer in the CN radical by frequency-modulated spectroscopy." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/62.
Full text
45
Kawachi, Tetsuya. "Plasma Spectroscopy of Highly Charged Ions by the Method of Collisional-Radiative Model." Kyoto University, 1995. http://hdl.handle.net/2433/160769.
Full textAbstract:
本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第6050号
工博第1447号
新制||工||990(附属図書館)
UT51-95-D369
京都大学大学院工学研究科物理工学専攻
(主査)教授 藤本 孝, 教授 大引 得弘, 教授 牧野 俊郎
学位規則第4条第1項該当
46
BAZALGETTE, COURREGES LACOSTE GREGORY. "Spectroscopie de tres haute resolution de icl. Photodissociation et collision de la molecule de icl orientee." Toulouse 3, 1997. http://www.theses.fr/1997TOU30224.
Full textAbstract:
Spectroscopie de tres haute resolution de icl : nous avons applique une technique de spectroscopie de saturation a la transition a-x de icl pour eliminer l'effet doppler residuel et determiner sa structure hyperfine. La faible largeur naturelle de cette transition confere a cette experience un interet metrologique. Les resultats que nous avons obtenu sur icl permettent de resoudre les structures hyperfines de l'iode et du chlore, contrairement a la technique de spectroscopie conventionnelle ou la structure du chlore est masquee par l'effet doppler residuel. Ces resultats sont interessants car la structure hyperfine moleculaire caracterise de maniere tres precise la liaison chimique. Photodissociation et collision de la molecule de icl orientee : h. J. Loesch a montre, en 1990, comment orienter l'axe moleculaire en appliquant un champ electrique intense sur des molecules polaires tres froides en rotation, produites par expansion supersonique. Plusieurs experiences de collisions ont ainsi ete realisees, mais l'orientation n'a jamais ete mesuree directement. Nous avons effectue une telle mesure sur un jet moleculaire de icl grace a une experience de photodissociation. Le jet de icl ensemence dans l'argon a ete optimise afin d'obtenir simultanement une tres basse temperature rotationnelle et une faible fraction de icl dans des complexes. Les atomes d'iode produits par la photodissociation et emis dans la direction du champ electrique sont detectes par spectrometrie de masse. Cette experience mesure l'orientation de l'axe moleculaire en fonction du champ applique et donne un acces direct au signe du moment dipolaire de icl dans l'etat x. Nous avons modelise l'experience par un calcul monte-carlo et mis en evidence d'importants effets non lineaires en champ electrique du processus d'orientation. D'autre part, nous avons etudie la theorie des effets de reorientation moleculaire lors d'une collision entre un atome et une molecule orientee par un champ electrique intense.
47
Boumsellek, Saïd. "Etude par spectroscopie d'électrons du processus d'ionisation dans les collisions d'atomes et d'ions négatifs avec des cibles atomiques et moléculaires." Paris 11, 1989. http://www.theses.fr/1989PA112188.
Full textAbstract:
Ce travail est une étude par spectroscopie d'électrons des processus d'excitation et d'ionisation dans les collisions de S et F avec les gaz rares : He, Ne, Ar, Kr et les molécules : H₂, 0₂, N₂, CO₂. Les résultats des collisions avec les ions négatifs correspondants sont aussi présentés afin d'étudier le détachement d'un et de deux électrons. Les spectres d'électrons montrent que la roduction des ions positifs S⁺ et F⁺ passe par la population d'états monoexcités autoionisants S(²D° nl et ²p° nl) et F(¹Dnl et ¹Snl). Ceci est une tendance générale des éléments à couche "p" ouverte. Une discussion des mécanismes aboutissant au détachement, à l'excitation et à l'ionisation, a lieu dans le cadre du modèle de promotion de Fano-Lichten utilisant une description quasi moléculaire de la collision. Cela indique que l'ionisation par le processus Auger quasi-moléculaire doit être l'autre mécanisme de production d'ions positifs. De point de vue spectroscopique des états autoionisants de type (coeur)np, inobservables dans les études de photoabsorption à cause des règles de sélection dipolaires, ont été identifiés. Dans le cas des cibles moléculaires, l'échange de charge vers une résonance de forme a été observé avec les ions négatifs. A la fois avec des projectiles neutres et des ions négatifs le processus d'ionisation dissociative a été observéResults of an electron spectroscopy study of excitation and ionisation processes in S and F collisions with He, Ne, Ar, Kr, H₂, 0₂, CO₂ are presented. Results of the corresponding negative ions (S-and F-) collisions are also presented to study the two- -electron detachment. The electron spectra indicate that singly excited autoionising states of S(²D° nl et ²p° nl) et F(¹Dnl et ¹Snl) and F(¹Dnl et ¹Snl) series are populated in these collisions and this should lead to an efficient mechanism of S+ and F+ production in the range of low energies. This is a general feature conceming elements with open "p" shell. Discussion of the mechanims leading to detachment, excitation and ionisation is presented in the frame work of the Fano-Lichten promotion model using a quasi-molecular description of the collision. This indicates that quasi-molecular Auger ionisation must be the other mechanism of positive ion production. Conceming the spectroscopie character previously unknown autoionising states of (core)np series are identified. These series are forbidden in photoabsorption measurements because of the dipole selection rules. In the case of molecular targets, charge exchange to shape resonances is observed with negative ions as projectiles. Both with neutra! species and negative ions dissociative ionisation is observed
48
Kolbe, G. "Three level spectroscopic technique applied to collision rate and line shape determination in a plasma." Thesis, Imperial College London, 1985. http://hdl.handle.net/10044/1/37746.
Full text
49
Sekhavat, Sépanta. "Planification de mouvements sans collisions pour systèmes non holonomes." Toulouse, INPT, 1996. http://www.theses.fr/1996INPT106H.
Full textAbstract:
Meme en l'absence d'obstacle la planification de mouvements pour un systeme non holonome (soumis a des contraintes cinematiques) n'est pas une tache aisee. L'evitement d'obstacle augmente encore la difficulte du probleme. Nous donnons une solution de ce probleme en combinant un planificateur geometrique sans collisions ignorant les contraintes non holonomes du systeme avec un planificateur local respectant ces dernieres contraintes mais ignorant les obstacles. Nous definissons une propriete topologique tp pour le planificateur local, traduisant la propriete de commandabilite locale du systeme. Nous montrons qu'avec un planificateur local respectant tp, il est possible de definir plusieurs strategies de planification globale exactes et completes. Nous prouvons qu'un tel planificateur local peut etre obtenu pour des systemes chaines, en appliquant des entrees sinusoidales. D'autre part nous construisons un nouveau planificateur local respectant tp pour un systeme plat particulier. Les strategies de planification globale sont illustrees par des applications aux systemes composes d'un chariot entrainant des remorques. En particulier, une experimentation reelle sur le robot hilare avec une remorque sur le site de laas-cnrs est presentee. Nous nous concentrons finalement sur les facteurs d'amelioration des performances calculatoires de la strategie de planification decouplant les contraintes geometriques et cinematiques. Cette etude donne naissance a un schema de planification multi-niveaux ou les contraintes non holonomes sont prises en compte progressivement par le biais de l'introduction de sous-systemes semi-holonomes. Des resultats obtenus par le planificateur associe sont presentes visant a illustrer l'amelioration des performances du planificateur de base
50
Ferraton, Mathieu. "Collisions profondément inélastiques entre ions lourds auprès du Tandem d’Orsay & Spectroscopie gamma des noyaux exotiques riches en neutrons de la couche fp avec le multi-détecteur germanium ORGAM." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112119/document.
Full textAbstract:
Les travaux effectués au cours de cette thèse au sein du groupe de structure nucléaire de l’IPN d’Orsay s’articulent autour de la production, en vue d’une étude par spectroscopie gamma, de noyaux exotiques riches en neutron de la couche fp. Dans ce cadre, nous avons mis en place, auprès de l’accélérateur Tandem d’Orsay, un multi-détecteur au germanium baptisé ORGAM, destiné à la spectroscopie gamma à haute résolution. Au cours de l’année 2008-2009, les détecteurs amenés à composer ORGAM ont été testés individuellement, ainsi que le dispositif annexe de réjection Compton, en coopération avec la division instrumentation du laboratoire. Parallèlement, le système d’alimentation automatique en azote liquide, destiné au maintien des détecteurs à basse température, a été amélioré et fiabilisé. L’ensemble du dispositif a été mis en place sur une ligne de faisceau de l’accélérateur tandem avec le concours du personnel technique de l’accélérateur.La première expérience utilisant le dispositif ORGAM a été réalisée en juillet 2009. Cette expérience, dont les données ont été analysées dans le cadre de ce travail, visait à étudier les collisions profondément inélastiques entre un faisceau de 36S accéléré à 154 MeV, et une cible de 70Zn. Un dispositif permettant la détection des particules chargées émises à grand angle a été utilisé afin d’identifier les fragments de ces collisions. Il n’a pas été possible, du fait du fond important induit par la diffusion élastique du faisceau dans la cible, d’identifier directement ces fragments. L’étude des coïncidences gamma-gamma avec le détecteur ORGAM a cependant permis de mettre en évidence de nombreuses cascades de photons désexcitant des noyaux potentiellement produits par les réactions d’intérêt.Les données recueillies au cours d’une autre expérience, réalisée auprès du tandem d’Orsay en 2005, ont été analysées dans le cadre de ce travail. Cette expérience, visant à produire par fusion évaporation entre un faisceau de 14C à 25 MeV et une cible de 48Ca, les noyaux de 59Mn et de 57Cr, a permis d’établir une partie du spectre en énergie d’excitation de ces noyaux, jusqu'à une énergie d’excitation supérieure à 3 MeV.Une étude théorique des noyaux de chrome impairs de la couche fp a été tentée à l’aide d’un modèle phénoménologique de couplage intermédiaire. Ce modèle a permis une description satisfaisante du 53Cr. Les prédictions du modèle, qui ne prend pas en compte l’interaction entre nucléons de valence, se sont avérées beaucoup moins satisfaisante pour les noyaux de 55Cr et 57CrThis PhD thesis was prepared within the nuclear structure group of IPN Orsay. The work presented aimed to produce neutron rich fp shell nuclei through heavy ion collisions at the tandem accelerator of IPN, and to study them using gamma spectroscopy. For this purpose, a germanium gamma array called ORGAM, and dedicated to high resolution gamma spectroscopy, was set up at the tandem accelerator. During the year 2008/2009, the individual germanium detectors were tested and repaired, as well as their ancillary anti-Compton shielding. At the same time, the liquid nitrogen auto-fill system was improved for better reliability. The array was finally set up on a beam line of the accelerator.The first experiment using the ORGAM array was performed in July 2009. This experiment aimed to study fully damped deep-inelastic collisions between a 36S beam accelerated to 154 MeV, and a 70Zn target. An additional charged particle detection system was used to detect interesting fragments emitted at backward angles. It was not possible to separate these fragments from the background induced by backscattered ions from the beam. Nevertheless, the study of gamma-gamma coincidences detected with the ORGAM array allowed to identify gamma cascades de-exciting nuclei potentially produced through the mechanism of interest. Data accumulated during another experiment performed at the tandem accelerator in 2005 were analyzed. Fusion-evaporation reaction between a 25 MeV, 14C beam focused on a 48Ca target produced the 57Cr and 59Mn nuclei, whose energy spectra were established up to 3 MeV.We attempted to study theoretically odd Chromium isotopes with a simple model based on the intermediate coupling scheme. This model, which doesn’t take into account correlation between valence nucleons, described in satisfactory way the semi-magic + 1 neutron, 53Cr, but failed to do so for mid-shell nuclei 55Cr and 57Cr