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Dissertations / Theses on the topic 'Photoionization'
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1
Bailey, Stephen Malcolm William. "Relativistic atomic photoionization." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387976.
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Hudson, C. E. "Photoionization of AlII." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268922.
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Hockett, Paul. "Photoionization dynamics of polyatomic molecules." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10857/.
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The work presented in this thesis was carried out with the ultimate aim of learning about the photoionization dynamics of polyatomic molecules. This is a complex problem; in order to obtain sufficient experimental data to shed light on the dynamics careful measurement of photoelectron angular distributions (PADs) is required. Ideally these measurements are rotationally-resolved, and the angular distributions measured correspond to the formation of the molecular ion in a single rotational state. The ionization event, in the dipole approximation, can be completely described by the dipole matrix elements. If sufficient experimental data to determine the radial components of the matrix elements and associated phases, the dynamical parameters, can be obtained the photoionization experiment may be said to be complete. Analysis of such experiments requires that the initial state of the molecular system is also known, to this end resonance-enhanced multi-photon ionization (REMPI) schemes can be used in order to populate a single quantum state prior to ionization. The experiments presented here follow this methodology, with various REMPI schemes used to prepare (pump) and ionize (probe) the molecule under study, and the velocity-map imaging (VMI) technique used to (simultaneously) record the photoelectron spectra and angular distributions. Two molecules have been studied experimentally, acetylene (C2H2) and ammonia (NH3). In both cases dynamical parameters pertaining to the formation of specific states (vibronic or vibrational) of the molecular ion have been determined from experimental data. Additionally, in the ammonia work, rotationally-resolved photoelectron images were obtained.
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Wilson, Nigel John. "Inner-shell photoionization and transition probabilities." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314150.
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Fisher, Barry Owen. "Soft X-ray photoionization of molecules." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394174.
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Alshorman, Mohammad. "Studies on K-shell photoionization of nitrogen ions and on valence photoionization of atomic and small molecular ions." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-00968031.
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In this thesis work, the K-shell photoionization of multi-charged ions has been studied as well as the valence photoionization of atomic and small molecular ions. The K-shell photoionization cross sections were measured for nitrogen iso-nuclear series, from N+ to N4+ ions using the ion-photon merged beam technique and the valence photoionization cross sections for Xe+ and Kr+ ions and the small molecular ions CO_2^+ and N_2^+ using both the merged beam and ion trap techniques at the SOLEIL synchrotron radiation facility in Saint-Aubin, France. Combination of the two techniques allows for the measurement of the pure ground state ionization cross section on an absolute scale.The experimental K-shell photoionization cross sections are compared with theoretical results obtained from the multi-configuration Dirac-Fock (MCDF), R-matrix and the Screening Constant by Unit Nuclear Charge (SCUNC) methods. The interplay between experiment and theory enables the identification and characterization of the strong 1s→2p and 1s→3p resonances observed in the spectra. The experimental valence photoionization cross sections for Xe+ and Kr+ ions are compared with MCDF calculations results obtained for the direct photoionization process. The quality of the absolute cross section measurements using the merged beam techniques is strongly dependent on the performance of Electron Cyclotron Resonance Ion Source (ECRIS). In order to improve the current of ions in the interaction region, the ions extraction system and transport was simulated by using IGUN program and ECRopt.
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Seabra, Gustavo De Miranda. "Electron propagator theory calculations of photoionization intensities /." Search for this dissertation online, 2005. http://wwwlib.umi.com/cr/ksu/main.
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Hennessy, Michael Joseph. "Photoionization of gases in the Extreme Ultraviolet." Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09SM/09smh515.pdf.
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Wang, Jing Cheng. "Photoionization and electron-impact ionization of Ar5+." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3221392.
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Alna'washi, Ghassan Ali. "Photoionization of Cl-Like K2+ and Ca3+." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3258836.
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Donnelly, David. "Inner shell photoionization of atoms and ions." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361243.
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Field, Thomas A. "Coincidence studies of reaction dynamics." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318622.
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Ramsbottom, Catherine Anne. "Photoabsorption by atoms and ions." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239229.
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Yu, Chin-hui. "Molecular photoionization calculations using the complex basis function method /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487586889187324.
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Matthews, Sarah Jane. "Near-threshold photodissociation and photoionization of triatomic molecules." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491378.
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Multichannel quantum defect theory (MQDT) has been used to simulate the doubleresonant autoionization spectra of HCO, produced following the photodissociation of acetaldehyde (CH3CHO). Vibrational angular momentum has been incorporated into these calculations for the first time. Simulations are produced for HCO involving Rydberg series with up to six quanta of ion-core bending mode (1I2) excitation. The simulation of resonances converging to the (0310) state of HCO+ is compared with our own experimentally recorded spectrum, while all other simulations are compared with spectra recorded by Grant et al. A good agreement between experimental and simulated spectra is reached, and values for both diagonal and off-diagonal quantum defect matrix elements for 1I2 = 0 - 6 are obtained and compared. A fully state selective velocity-map ion imaging (VMI) study of N02 photodissociation was carried out over a range of photolysis wavelengths. Images were recorded for three different rotational channels of NO (JII = 3/2, 11/2 and 21/2) and different spin-orbit states of the 0 atom (3P2,1), at photolysis energies ranging from 0 to 1000 cm-1 above the dissociation threshold. The angular anisotropy parameter (fJ) was then obtained as a function of both excess energy Eexc (energy above threshold) and available energy Eavl (Eexc - Erot ). The observed variation in the angular anisotropy parameter fJ close to the dissociation threshold is explained by considering the dissociation mechanism of N02 • After initial excitation to the A state, non-adiabatic coupling means that dissociation actually occurs on the ground potential energy surface. The reaction rate constants fluctuate rapidly in this energy region and level out at higher excess energies. These fluctuations in reaction rates have a strong effect on the angular distribution of the photofragments and translate directly into the wide variations of fJ observed in this work. The range of lifetimes derived from these spectra are in agreement with the range observed in picosecond pump-probe experiments.
16
Li, Hui. "Study on molecular photoionization in femtosecond laser field." Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/15913.
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Master of Science<br>Department of Physics<br>Matthias Kling<br>This thesis consists of two major parts. The first part concerns studies of the orientation dependence of the ionization of diatomic molecules in intense, femtosecond two-color laser fields. The second part is about studies on the ionization mechanisms of the C[subscript]6[subscript]0 molecule in femtosecond near-infrared and ultraviolet laser fields.
In the first part, experimental and theoretical results on the asymmetric ion emission of the heteronuclear molecules CO and NO in two-color laser fields are discussed. The two-color fields, which can be tailored by a relative phase, are used to ionize and dissociate CO and NO molecules, both of which are molecules with small polarizabilities. The resulting C[superscript]+, C[superscript]2[superscript]+, N[superscript]+ and O[superscript]+ ions are detected by a velocity map imaging (VMI) setup. The photoelectrons from above-threshold ionization (ATI) of Xe are studied under such a two-color field to assign the phase. For both CO and NO we find that enhanced ionization occurs when the molecule is oriented with the electric field pointing from the C or N atom toward the O atom. This is in agreement with the molecular orbital Ammosov-Delone-Krainov (MO-ADK) theory and the Stark-corrected strong-field-approximation (SFA) calculations.
The second part is devoted to the investigation of the ionization mechanism of neutral C[subscript]6[subscript]0 molecules with 30 fs laser pulses at about 800 nm and with 50 fs pulses at about 400 nm. The angular distributions of photoelectrons are measured utilizing VMI. Measurements under different intensities are carried out for the two wavelengths. In our work, thermal electron emission is highly suppressed by the use of short pulses. For near-infrared excitation, photoelectron angular distributions (PADs) that contain six lobes are observed for low energy electrons. This behavior is different from studies for longer pulses of about 120 fs [1]. Further analysis indicates that the PADs might originate from single photon ionization of a super atomic molecular orbital (SAMO), however, a detailed assignment requires further theoretical work. The PADs for the ultraviolet excitation show very similar structures to earlier results [1]. For the near-infrared excitation, we have carried out studies as a function of the chirp of the pulses and find effects on photoelectron spectra and on PADs, which are tentatively explained by sequential multiphoton ionization via “doorway” states.
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QUADRI, NICOLA. "THEORETICAL STUDY OF PERTURBATIVE AND NON-PERTURBATIVE PHOTOIONIZATION." Doctoral thesis, Università degli Studi di Trieste, 2018. http://hdl.handle.net/11368/2918470.
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Photoionization processes have been examined from a theoretical perspective with the aim of increasing the number of the describable phenomena involved in such processes. This aim has been achieved by the implementation of several algorithms based on the use of B-splines as basis functions to treat both correlation effects and non-perturbative photoionization regime.
The first part of the thesis is dedicated to correlation effects within the bound states. Since a standard DFT method does not permit to study any correlation effect, we present a single channel approach that uses Configuration Interaction (CI) to describe both the neutral initial state and ionic final state. More specifically, this method applies a Complete Active Space Self-Consistent Field (CASSCF) procedure to treat such correlation effects. Ionization potentials are further improved by n-electron valence state perturbation theory (NEVPT2). Dyson orbitals are used in this context to calculate the dipole transition moments. The most frequent evidence of electron correlation is the presence of additional bands, called satellite bands, in the photoelectron spectra. The structure and the position of satellite bands in some diatomic molecules has been studied. For all the considered molecules, dynamical photoionization observables have been calculated for the first ionization states, by comparing the results so obtained to those ones got by standard DFT method, Dyson orbital approach and HF method. The formalism has been also applied to the O_3 molecule within a collaboration that aimed to obtain the time-resolved photoelectron spectrum of this molecule.
In the second part of the thesis, the implementation of an algorithm to calculate two-electron integrals in the LCAO B-spline basis with the aim to treat all the many-electron effects is illustrated. This has been done to fully express the final wavefunction within the so called Close-Coupling (CC) formalism that permits to also describe correlation effects involving continuum states. In particular, two-electron integrals have been calculated by solving the Poisson equation relative to the first charge density and integrating the resulting potential with the second charge density. The results are compared to the corresponding integrals obtained by using MOLPRO quantum chemistry package.
The third part of the thesis presents a method to treat the non-perturbative phenomena by solving Time-Dependent Schrödinger Equation (TDSE). In this method, time-evolution is discretized in subintervals sufficiently small so that the Hamiltonian approximately becomes time-independent. The final wavepacket, derived by time propagation, is then projected onto the continuum states calculated with the DFT method. Photoelectron spectra and MFPADs are obtained for several systems, such as hydrogen atom, H_2^+, NH_3 and H_2 O.
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Johnson, Alexander Spencer. "Photoionization of atoms in parallel electric and magnetic fields." Thesis, Royal Holloway, University of London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343603.
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Downie, Peter. "Photoionization of oriented molecules : angle resolved photoelectron photoion coincidence." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243490.
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Dierking, Christoph Wilhelm Hansjörn Ralf. "Photoionization and vibrational spectroscopy of sodium doped water clusters." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2019. http://hdl.handle.net/11858/00-1735-0000-002E-E608-3.
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Moretti, Francesco. "A Model Investigation of Photoionization Delay for Atomic Clusters." Thesis, Stockholms universitet, Fysikum, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-159523.
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Lebech, Mogens. "Vector correlations in dissociative photoionization of small polyatomic molecules." Paris 11, 2003. http://www.theses.fr/2003PA112007.
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La photoionisation dissociative de petites molécules polyatomiques, ici N20 et CO2, induite par rayonnement synchrotron VUV polarisé linéairement est étudiée par la méthode des corrélations vectorielles, dans les conditions où la photoionisation conduit à un ion, un fragment neutre et un électron. Celle-ci consiste à mesurer les vecteurs vitesses du photoion et du photoélectron produits par chaque événement. Le spectromètre des vitesses utilise la détection en coi͏̈ncidence de l'ion et de l'électron résolue en temps-de-vol et sensible en position. Les particules chargées sont extraites de la zone d'interaction par un champ électrique uniforme, qui en assure une collection complète. Deux lentilles électrostatiques ont permis d'améliorer la résolution des vecteurs vitesses. Le diagramme de corrélation des énergies cinétiques ion-électron déduit des amplitudes des vecteurs vitesses permet d'identifier le chemin réactionnel pour chaque processus par l'état intermédiaire de valence de N20+ ou CO2+, ou l'état autoionisant N20**, et la limite de dissociation caractérisée par l'état électronique des deux fragments et la distribution vibrationnelle du fragment moléculaire. La corrélation spatiale des deux vecteurs vitesses et de l'axe de la polarisation de la lumière conduit, pour chaque processus, à la dépendance polaire et azimutale de la distribution angulaire des photoélectrons dans le référentiel moléculaire, pour chaque orientation de l'axe moléculaire par rapport à la polarisation. Pour chaque processus les résultats sont représentés par quatre fonctions Fij, qui contiennent l'information la plus complète sur la dynamique de la photoionisation : leur analyse en ondes partielles donne accès aux moments de transition. Pour plusieurs réactions identifiées, la distribution angulaire des photoélectrons dans le référentiel moléculaire présente des anisotropies. Certains résultats obtenus pour N20 sont comparés avec des calculs 'multichannel Schwinger configuration interaction'<br>Dissociative photoionization of small polyatomic molecules, here N20 and CO2, induced by VUV linearly polarized synchrotron radiation is studied using the vector correlation method, in conditions where photoionization leads to one ion, one neutral fragment, and one electron. The vector correlation method consists in measuring the velocity vectors of the photoion and photoelectron produced in each event. The velocity spectrometer combines time-of-flight resolved and position sensitive ion-electron coincidence detection. Ions and electrons are extracted from the interaction zone by a uniform electric field, which ensures a complete collection of both particles. Electrostatic lenses are implemented in the spectrometer in order to increase the velocity vector resolution. The ion-electron kinetic energy correlation derived from the magnitude of the velocity vectors for the coincident events allows one to identify the reaction pathway for each process, in terms of the intermediate N2O+ or CO2+ valence or inner-valence ionic state, or resonant N20** autoionizing state, and the dissociation limit characterized by the electronic states of both fragments and the vibrational distribution of the molecular fragment. The spatial analysis, correlating the two velocities and the polarization axis of the light, determines, for each process, the polar and azimuthal dependence of the molecular frame photoelectron angular distribution, for any orientation of the molecular axis with respect to the polarization axis. The results are presented in terms of four Fij functions which contain the most complete information about the photoionization dynamics for each process: their partial wave analysis gives access to the transition moments. A large number of reactions are identified, and anisotropies in the photoelectron angular distribution in the molecular frame are observed. Selected results obtained for N2O are compared with multichannel Schwinger configuration interaction calculations
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Ponzi, Aurora. "Theoretical study of molecular photoionization: diffraction and correlation effects." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11112.
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2013/2014<br>Questa tesi raccoglie i risultati dell’attività di ricerca del mio dottorato che ha
riguardato lo studio di molecole sottoposte a fotoionizzazione e il calcolo delle
grandezze dinamiche coinvolte in questo tipo di processo. Una prima linea di
ricerca ha seguito la descrizione degli effetti di interferenza e diffrazione nei profili
di fotoionizzazione ad alte energie, attraverso un approccio basato sul metodo
Density Functional Theory (DFT) accoppiato all’uso di una base di B-spline. Le
oscillazioni derivanti da questi effetti di interferenza e diffrazione rappresentano
un fenomeno universale, presente in tutte le molecole poliatomiche in esame, dalle
biatomiche a quelle più complesse non simmetriche, dalla shell di core a quella
di valenza più esterna. Nella regione di core abbiamo analizzato le oscillazioni
presenti nel rapporto di intensità C2,3/C1,4 nello spettro di fotoelettone C 1s del
2-butino. Nella regione di valenza più interna abbiamo invece preso in esame gli
spettri di fotoionizzazione di semplici molecole poliatomiche (propano, butano,
isobutano e cis/trans-2-butene) e i risultati ottenuti sono stati confrontati con
quelli sperimentali raccolti presso il sincrotrone Soleil di Parigi. Abbiamo poi
analizzato l’effetto dovuto all’emissione coerente da centri equivalenti e quello
dovuto alla diffrazione da atomi vicini non equivalenti negli spettri di core e di
valenza. Nell’ambito di questa analisi, abbiamo preso in esame acetileni mono e
disostituti con fluoro e iodio, comparando i risultati con quelli ottenuti nel caso
del più semplice sistema acetilenico. Ci siamo inoltre occupati dello studio di effetti
di intereferenza nella ionizzazione di valenza esterna di semplici idrocarburi
e, nella stessa regione, abbiamo analizzato come la struttura geometrica di composti
permetilati, in particolare la distanza metallo-anello, influenzi i loro profili
di fotoionizzazione. Infine, nella regione di valenza interna, sono stati considerati i
profili di ionizzazione per il caso di Ar@C60. I risultati sono stati messi a confronto
con quelli ottenuti da uno studio precedente sulla molecola di C60. Una seconda linea di ricerca ha invece seguito la descrizione delle osservabili
di fotoionizzaione considerando il contributo della correlazione elettronica.
Questo può essere fatto attraverso l’implementazione di un formalismo closecoupling
dove la funzione del continuo finale è espressa secondo un’espansione
analoga a quella Configuration Interaction (CI) per gli stati legati. Il primo livello
dell’implementazione ab initio è stato quello di descrivere accuratamente solo la
correlazione negli stati legati. A questo scopo, sono stati utilizzati gli orbitali di
Dyson. L’uso di questi orbitali è stato applicato alla descrizione delle osservabili
di fotoionizzazione nel caso della molecola biatomica CS. Nello spettro di questa
molecola è infatti presente un satellite ben risolto dovuto a effetti di correlazione
elettronica che non possono essere descritti a livello DFT.<br>The thesis is focused on the study of the dynamics of photoemission processes
for atoms and molecules. A first line of research has followed the description of
diffraction and interference effects in the photoionization profiles at high energy
for several systems, through an approach based on the DFT method combined
with the use of a B-spline basis. These diffraction and interference effects appear
in the spectra as a result of wave propagation. The resulting oscillations
represent a general phenomenon, present in polyatomic targets, from diatomics to
complex non-symmetrical molecules, and from the deep core to the outer-valence
shell. Firstly, in the core region, we analysed the oscillations in the intensity ratio
C2,3/C1,4 in the carbon 1s photoelectron spectrum for 2-butyne. Then in the
inner-valence shell region, the interference effects in the photoionization spectra of
simple polyatomic molecules (propane, butane, isobutane and cis/trans-2-butene)
were studied and the results have been compared with experimental data collected
at the SOLEIL Synchrotron in Paris.
Furthermore, we have analysed the effect due to coherent emission from equivalent
centers and diffraction from neighbouring non-equivalent atoms in core and
valence photoelectron spectra. For this, we investigated mono and disubstituted
fluoro- and iodo-acetylenes and compared them to the simple acetylene system.
We also focused on interference effects in the outer-valence ionization cross sections
of simple hydrocarbons and, in the same shell, we also studied the influence
of geometrical structures on photoionization profiles of permethylated compounds.
Finally, in the inner-valence shell region, we considered the photoionization profiles
for the case of Ar@C60. The results were compared with a previous study on
the C60 molecule. A second line of research has followed the correlated description of photoionization
observables. We developed a new method based on an ab initio closecoupling
formalism. The use of the Dyson orbitals allowed to study the photoemission
observables of highly correlated systems. As a first application of this
method, we performed highly correlated calculations on the primary ionic states
and the prominent satellite present in the outer-valence photoelectron spectrum
of CS. Dyson orbitals are coupled to accurate one-particle continuum orbitals to
provide a correlated description of energy-dependent cross sections, asymmetry
parameters, branching ratios and Molecular Frame Photoelectron Angular Distributions
(MFPADs).<br>XXVII Ciclo<br>1985
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Navea, Juan G. Manzanares Carlos E. "Studies on the application of laser photoionization in supersonic-jets for the generation of intense ionic clusters." Waco, Tex. : Baylor University, 2006. http://hdl.handle.net/2104/4878.
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Elwert, Torsten August Wilhelm Heinrich. "Photoionization models of the diffuse ionized gas in galactic halos." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970369166.
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Rolles, Daniel. "Scattering and coherence phenomena in the photoionization of small molecules." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975198572.
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Chen, Yanfeng. "Analysis of Biological Molecules Using Stimulated Desorption Photoionization Mass Spectrometry." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14620.
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Surface-assisted laser desorption/ionization mass spectrometry (SALDI MS) is a novel technique for direct analysis of organic and biological molecules. Amino acids, dipeptides, and organoselenium compounds were successfully detected by SALDI on carbon and silicon surfaces. Surface effects, solvent effects, temperature effects and pH effects were studied. A possible mechanism of SALDI is proposed based on observed results.
In general, stimulated desorption results in neutral yields that are much larger than ion yields. Thus, we have exploited and further developed laser desorption single photon ionization mass spectrometry (LD/SPI MS) as a means of examining biomolecules. The experimental results clearly demonstrate that LD/SPI MS is a very useful and fast analysis method with uniform selectivity and high sensitivity.
Selenium (Se) is an essential ultra-trace element in the human body. In efforts to obtain more useful information of selenium metabolites in human urine, mass determination of unknown organoselenium compounds in biological matrices using SALDI MS was investigated. In another approach, several selenium metabolites in human urine were successfully detected by LD/SPI MS. A HPLC-MS/MS method was also developed for a quantitative case study of selenium metabolites in human urine after ingestion of selenomethionine.
Low-energy electrons (LEE, 3-20 eV) have been shown to induce single and double strand breaks (SSB and DSB) in plasmid DNA. To understand the genotoxic effects due to secondary species of high-energy radiation, we investigate the role of transient negative ions and the specificity in LEE-DNA damage by examining the neutral product yields using low electron stimulated dissociation SPI MS. The neutral yields as a function of incident electron energy are also correlated with the SSBs and DSBs measured using post-irradiation gel electrophoresis. The results provide further insight concerning the mechanisms of LEE-induced damage to DNA.
Overall, this research provided an in-depth understanding of non-thermal surface processes and the development of new mass spectrometric techniques for the analysis of biomolecules.
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Onoda, Yugo. "Trapping of Yb+ Loaded through Photoionization in RF Ion Trap." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/152515.
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Lu, Miao. "Photoionization and electron-impact ionization of multiply charged krypton ions." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3221392.
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Quigley, Lisa Maria. "Applications of atomic R-matrix theory to resonances and photoionization." Thesis, Queen's University Belfast, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388175.
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Zhu, Yang. "Photoionization spectroscopy of high-lying even-parity levels in iron /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487686243822878.
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Habibi, Mustapha. "Photoionization of the cerium isonuclear sequence and cerium endohedral fullerene." abstract and full text PDF (UNR users only), 2009. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3355583.
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HUTH, THOMAS CARL. "ANALYTICAL MASS SPECTROMETRY WITH A SELECTIVE VACUUM ULTRAVIOLET PHOTOIONIZATION SOURCE." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183916.
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The vacuum ultraviolet molecular hydrogen laser is evaluated as a selective ion source for analytical mass spectrometry of easily-ionized compounds. The types of compounds ionized below the photon energy of 7.8 eV include polynuclear aromatic hydrocarbons, and many amines and nitrogen-containing heterocycles. The latter two categories encompass a large number of pharmaceuticals and drugs of abuse. H₂ laser photoionization produces parent molecular ions only, for all compounds studied thus far. Selectivity of the threshold photoionization process is very high, as compounds within as little as 0.2 eV above the threshold are completely rejected. The ability of the technique to discriminate against interfering matrix components is demonstrated for both simple synthetic and complex "real world" mixtures. Easily interpreted spectra are obtained from simple extracts of spiked coffee, beer, soy sauce, urine and blood serum. The most important interference is shown to be electron impact ionization arising from acceleration of stray electrons in the ion source. Most of this ionization is caused by low-energy secondaries generated when stray primaries are collected by the ion source electrodes. The primaries are produced mainly by interaction of scattered laser radiation with metal surfaces. This interference can be controlled through proper instrumental design.
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Nemeth, Gregory Richard Alexander James. "Multi-electron dynamics investigated with strong-field tunnelling and XUV photoionization." Thesis, Swansea University, 2011. https://cronfa.swan.ac.uk/Record/cronfa42905.
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Hatherly, P. A. "The multiphoton multiple ionization of molecules." Thesis, University of Reading, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234654.
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Morgan, Ross Alexander. "Resonance enhanced multiphoton ionisation spectroscopy of sulphur containing molecules." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337177.
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Howes, Neil Uist Macdonald. "Kinetic and mechanistic studies in atmospheric chemistry using photoionization mass spectrometry." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15766/.
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The aim of this thesis is to provide updated, accurate kinetic (and where possible mechanistic) information regarding the oxidation pathways of various volatile organic compounds (VOCs) and trace gas species within the troposphere. The vast majority of the experiments discussed were conducted using a pulsed laser photolysis, photoionization mass spectrometry (PLP-PIMS) set-up, which operated at low pressures (p = 2 Torr). PLP-PIMS is a time-resolved technique can be used to directly monitor multiple species simultaneously and with time; details of this method are found in Chapter II. Initially, one shortcoming of the PLP-PIMS technique was that it could not detect OH radicals (due to the ionization potential of OH). However, in Chapter III a 1 + 1’ multiphoton ionization (MPI) scheme was implemented, making OH detection possible. In Chapter IV, kinetic and mechanistic information regarding the oxidation of acetaldehyde, CH3CHO, by OH is reported. From this study a rate coefficient of kOH = (1.6 ± 0.2) × 10-11 cm3 molecule-1 s-1 was measured, this is in good agreement with other literature values. Additionally, it was observed that a small yield of methyl radicals (YCH3 ≈ 15%) was also produced. Methyl radicals were an unexpected product from this reaction and it is hypothesised that they are formed from the dissociation of nascent, chemically activated acetyl radicals. Notably, the yield of methyl radicals observed is significantly lower than would be expected from a statistical distribution of the energy between the products. Therefore, a post-reaction complex is proposed to allow for the redistribution of energy. In Chapters VI, reactions of the C1 and C2 Criegee intermediates (CH2OO and CH3CHOO, respectively) with SO2 and NO2 are reported. For the C1 Criegee intermediate (CI), rate coefficients of kC1SO2 = (3.8 ± 0.3) × 10-11 cm3 molecule-1 s-1 and kC1NO2 = (1.2 ± 0.3) × 10-12 cm3 molecule-1 s-1 are reported for the reactions with SO2 and NO2 respectively. For the C2 CI, rate coefficients of kC2SO2 = (1.8 ± 0.3) × 10-11 cm3 molecule-1 s-1 and kC2NO2 = (7.0 ± 1.6) × 10-13 cm3 molecule-1 s-1 were measured. Moreover, in the C2 CI + SO2 reaction, acetaldehyde was positively identified as a product from this reaction at low pressures. Finally, in Chapter VII the reactivity of Criegee intermediates towards different organic species was investigated. From these experiments it was observed that the C1 CI had significant rate coefficients with carboxylic acids, and rate coefficients of kC1FA = (3.7 ± 0.6) × 10-11 cm3 molecule-1 s-1 and kC1AA = (7.1±1.1) × 10-11 cm3 molecule-1 s-1 measured for the reactions with formic and acetic acid, respectively. However, the reactivity of CIs towards alkenes is thought to be considerably slower with upper limits of kC1ethene < 2 × 10-14 cm3 molecule-1 s-1 and kC1isoprene < 3 × 10-13 cm3 molecule-1 s-1 measured for the reactions of the C1 CI with ethene and isoprene.
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Ashmore, Jonathan P., and n/a. "Laser Cooling and Trapping of Metastable Neon and Applications to Photoionization." Griffith University. School of Science, 2005. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20060202.153538.
Full textAbstract:
This thesis presents an in-depth study into the characterization and enhancement of a metastable neon laser cooled and trapped atomic beam. The apparatus consists of a standard Zeeman slowed atomic beam loaded into a magneto-optical trap and was designed for applications to electron scattering experiments and photoionization. The efficiency of the metastable neon atomic source was investigated to determine the ideal cathode type for maximum metastable production and optimal atomic beam velocity haracteristics. A series of characterization measurements were performed on the MOT, and the trap volume and population were investigated for a range of trapping and slowing laser intensities and detunings, together with the MOT and Zeeman slower magnetic fields. The volume measurements were compared to standard Doppler theory and it was found that the Doppler model inadequately explained the trap behaviour. It was found that the MOT population characteristics were governed by two processes: two-body losses that limit the trap population at high densities, and the efficiency of the atom capture process which limits the operational range of the MOT over the various parameters. The trap temperature was determined to be 1.3mK via a time-of-flight technique. This was nearly twice that predicted by Doppler theory and the lack of agreement once again suggests the inadequacies in the Doppler theory to correctly model the experiment. The application of the MOT to the photoionization cross-section measurement of the (2p53p)3D3 state of neon was investigated. The MOT decay technique was utilized to measure cross-section values of o351 = 2.9+0.2 -0.3 x 10 -18cm2 and o363 = 3.1 +0.3 -0.4 x 10-18cm2 at the wavelengths of 351nm and 363nm respectively. This is an increase in accuracy of around a factor of five from previous measurements and it was found that the results agreed well with the values predicted by current theories.
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Mysak, Erin R. Baer Tomas. "Gentle photoionization of organic constituents using vacuum ultraviolet aerosol mass spectrometry." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2006. http://dc.lib.unc.edu/u?/etd,592.
Full textAbstract:
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2006.<br>Title from electronic title page (viewed Oct. 10, 2007). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.
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sossah, ayao m. "Photoionization of the Potassium Isoelectronic Sequence: Ca+ and Transition Metal Ions." Digital Archive @ GSU, 2010. http://digitalarchive.gsu.edu/phy_astr_diss/44.
Full textAbstract:
Photoionization cross section calculations are performed for the ground ([Ne]3s23p63d 2D ) and the first two excited ([Ne]3s23p63d 2D and [Ne]3s23p64s 2S ) states of potassium-like transition metal ions (Sc+2, Ti+3, V+4, Cr+5, Mn+6, Fe+7), along with photoionization calculations for K-like Ca+ ions in the ground ([Ne]3s23p64s 2S ) state and the first two excited ([Ne]3s23p63d 2D and [Ne]3s23p63d 2D ) states. The discrete N-electron final state ion system orbitals are generated using the computer program AUTOSTRUCTURE; 24 configurations are included in the configuration-interaction (CI) calculation for transition metal ions, and 30 configurations for the case of Ca+ ions. The initial and final (N+1)-electron wavefunctions are generated using R-matrix along with photoionization cross sections. In addition to the non-relativistic (LS-coupling) R-matrix, we have used the relativistic (Breit-Pauli) R -matrix method to carry out these calculations to focus on relativistic effects. Relativistic and non-relativistic results are compared to demonstrate the influence of relativistic effects. The prominent 3p → 3d giant resonances are analyzed and identified, and our calculated positions and widths are compared with experimental results for K-like ions such as Ca+, Sc+2 and Ti+3. In the case of lower Z (22 Z 20) ions (Ca+, Sc+2 and Ti+3), the photoionization cross section spectra are dominated by the giant (3p 3d excitation) resonances, while in cases of higher Z (26 Z 23) ions (V+4, Cr+5, Mn+6 and Fe+7), the 3p 3d resonances lie below the ionization threshold, and the cross sections are dominated by 3p53d nd and 3p53d n’s Rydberg series of resonances. Comparison of the Ca+, Sc+2 and Ti3+ results with available theoretical and experimental data shows good agreement.
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Daly, Steven. "Study of the photoionization of chiral molecules using polarized VUV radiation." Thesis, University of Nottingham, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.594763.
Full text
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Ashmore, Jonathan P. "Laser Cooling and Trapping of Metastable Neon and Applications to Photoionization." Thesis, Griffith University, 2005. http://hdl.handle.net/10072/367728.
Full textAbstract:
This thesis presents an in-depth study into the characterization and enhancement of a metastable neon laser cooled and trapped atomic beam. The apparatus consists of a standard Zeeman slowed atomic beam loaded into a magneto-optical trap and was designed for applications to electron scattering experiments and photoionization. The efficiency of the metastable neon atomic source was investigated to determine the ideal cathode type for maximum metastable production and optimal atomic beam velocity haracteristics. A series of characterization measurements were performed on the MOT, and the trap volume and population were investigated for a range of trapping and slowing laser intensities and detunings, together with the MOT and Zeeman slower magnetic fields. The volume measurements were compared to standard Doppler theory and it was found that the Doppler model inadequately explained the trap behaviour. It was found that the MOT population characteristics were governed by two processes: two-body losses that limit the trap population at high densities, and the efficiency of the atom capture process which limits the operational range of the MOT over the various parameters. The trap temperature was determined to be 1.3mK via a time-of-flight technique. This was nearly twice that predicted by Doppler theory and the lack of agreement once again suggests the inadequacies in the Doppler theory to correctly model the experiment. The application of the MOT to the photoionization cross-section measurement of the (2p53p)3D3 state of neon was investigated. The MOT decay technique was utilized to measure cross-section values of o351 = 2.9+0.2 -0.3 x 10 -18cm2 and o363 = 3.1 +0.3 -0.4 x 10-18cm2 at the wavelengths of 351nm and 363nm respectively. This is an increase in accuracy of around a factor of five from previous measurements and it was found that the results agreed well with the values predicted by current theories.<br>Thesis (PhD Doctorate)<br>Doctor of Philosophy (PhD)<br>School of Science<br>Full Text
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Homan, Mark Eugene. "A krypton VUV photoionization source for gas chromatography and mass spectrometry." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185223.
Full textAbstract:
The use of a coaxial krypton discharge lamp to selectively photoionize samples in a complex matrix is described. The lamp produces a krypton line emission spectrum with available photon energies of 10.0 and 10.6 eV. When used as a photoionization mass spectrometer source, conditions can be created where molecular ions can be produced which do not undergo fragmentation. This effect can greatly simplify spectral interpretation in the case of either direct sample introduction or coelution from a chromatographic column. Mixtures containing 6 to 8 components can be analyzed by direct injection with detection limits for most of the components below the 100 x 10⁻⁹ g level. Data is also presented demonstrating the lamps ability to switch between photoionization conditions producing primarily molecular ions and conditions producing spectra similar to those produced by electron impact sources. This ability would allow two complimentary sets of mass spectrometric information to be gathered during a single run. Using the lamp as a photoionization GC detector, a LOD of 12 x 10⁻¹² g for benzene has also been determined.
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Chatzipetros, Argyrios. "A simple model of above threshold ionization." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42087.
Full text
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Mah, Kelly Robert Lim. "Investigations of resonantly enhanced multiphoton ionizations of atomic mercury and potassium." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26451.
Full textAbstract:
Two investigations are reported on the application of resonantly enhanced multiphoton ionization (RMPI) to gaseous mixtures of an atomic vapor and a few Torr of argon. Photon fluxes large enough to ionize atoms by RMPI were produced by focussing down the light from a tunable pulsed dye laser. The irradiances generated were of the order of 500MWcm⁻². Ionization was detected by a voltage biased wire electrode that simply collected the photoelectrons either directly or after some gas multiplication. One investigation was the measurement of the dependence of RMPI processes in mercury on the polarization of the incident light for comparisons with theoretical calculations. The processes were four-photon resonant absorptions to either a ¹S₀ or ¹’³D₂ level followed by single photon ionization. Complete photoionization of all atoms excited to the resonant levels is established and the measured polarization dependences are found to agree with the calculated polarization dependence for the resonant excitation step of the RMPI process. Unexplained observations of the distortions in the polarization dependence of the ion yield and the absorption linewidth of the 6d ¹D₂ resonance are discussed. The second investigation was a study of the density dependent electric dipole forbidden two-photon resonant transition ²S → ²P in three-photon RMPI spectra of the Rydberg states of potassium. Stark interactions are shown to be unlikely and too weak. From the characteristics of the spectra, the excitation process is identified as a laser-assisted collision interaction.<br>Science, Faculty of<br>Physics and Astronomy, Department of<br>Graduate
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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.<br>Science, Faculty of<br>Chemistry, Department of<br>Graduate
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Chu, Wei-Chun. "Photoionization of the Be Isoelectronic Sequence: Relativistic and Nonrelativistic R-Matrix Calculations." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/phy_astr_diss/40.
Full textAbstract:
The photoionization of the beryllium-like isoelectronic series has been studied. The bound state wave functions of the target ions were built with CIV3 program. The relativistic Breit-Pauli R-matrix method was used to calculate the cross sections in the photon energy range between the ionization threshold and 1s24f7/2 threshold for each ion. For the total cross sections of Be, B+, C+2, N+3, and O+4, our results match experiment well. The comparison between the present work and other theoretical works are also discussed. We show the comparison with our LS results as it indicates the importance of relativistic effects on different ions. In the analysis, the resonances converging to 1s22lj and 1s23lj were identified and characterized with quantum defects, energies and widths using the eigenphase sum methodology. We summarize the general appearance of resonances along the resonance series and along the isoelectronic sequence. Partial cross sections are also reported systematically along the sequence. All calculations were performed on the NERSC system.
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Yang, Chieh Jen. "New Correlation Effects in Nonrelativistic Atomic Photoionization in the High Energy Limit." Digital Archive @ GSU, 2005. http://digitalarchive.gsu.edu/phy_astr_theses/1.
Full textAbstract:
The effect of initial state correlation on high-energy dipole photoionization is considered and it is shown that for almost all atomic electron the asymptotic high-energy dependence is E-7/2, and the dominant transition is an ionization plus excitation satellite transition. This is demonstrated in numerical calculations of the photoionization of Ge4p2 1S and Sn 5p2 1S.
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Smith, Derek Robert. "Systematic study of dopants for use in atmospheric pressure photoionization mass spectrometry." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/5649.
Full textAbstract:
Atmospheric pressure photoionization (APPI) is an effective ionization technique for the
analysis of low polarity and nonpolar compounds using liquid chromatography/mass
spectrometry. Ions are produced through a mechanism which begins with initial
photoionization of a primary reagent, termed a "dopant", followed by either proton
transfer or charge exchange with the analyte(s). This thesis regards improving the
ionization efficiency of APPI by identifying new dopant candidates that can increase the
breadth of compounds amenable to APPI, and/or improve the ionization efficiency for
compounds that are already amenable to APPI. The desired properties for a dopant
candidate include high ionization energy (IE) and low reactivity of its photoions with
solvent and dopant neutrals. Reactivity tests for 25 substituted-benzene compounds with
substituents ranging from strongly electron withdrawing (EW) to strongly electron
donating (ED) were performed. Results showed that ED groups decreased reactivity and
IE while EW groups increased reactivity and IE; an exception was if the ED group was
itself acidic. Of the compounds tested, 2,4-difluoroanisole and 3-(trifluoromethyl)anisole
showed the best potential as dopants for charge exchange. These dopants - along with
two other novel dopants, bromo- and chlorobenzene - were compared with established
dopants (toluene, anisole, and a toluene/anisole mixture) for charge exchange ionization
of polycyclic aromatic hydrocarbons (PAHs). Bromo- and chlorobenzene both showed
significant improvement in ionization efficiency compared with previously established
dopants due to their relatively low reactivity with the solvent and high IE. It was also
found that the improved performance for higher IE PAHs, when using anisole, diluted to
0.5% with toluene, was possibly due to the presence of an impurity in anisole. Of the
dopants tested, bromobenzene/2,4-difluoroanisole (99.5:0.5 v/v) was determined to be the
best overall for charge exchange ionization.
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Fanis, Alberto De. "Double photoionization of alkaline earth atoms and photoelectron spectroscopy of reactive intermediates." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327255.
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