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Photoionization

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Articles 1 - 30 of 83

Full-Text Articles in Physical Sciences and Mathematics

Analytical Results For The Three-Body Radiative Attachment Rate Coefficient, With Application To The Positive Antihydrogen Ion H¯+, Jack C. Straton Apr 2020

Analytical Results For The Three-Body Radiative Attachment Rate Coefficient, With Application To The Positive Antihydrogen Ion H¯+, Jack C. Straton

Physics Faculty Publications and Presentations

To overcome the numerical difficulties inherent in the Maxwell–Boltzmann integral of the velocity-weighted cross section that gives the radiative attachment rate coefficient αRA for producing the negative hydrogen ion H or its antimatter equivalent, the positive antihydrogen ion H¯+ , we found the analytic form for this integral. This procedure is useful for temperatures below 700 K, the region for which the production of H¯+ has potential use as an intermediate stage in the cooling of antihydrogen to ultra-cold (sub-mK) temperatures for spectroscopic studies and probing the gravitational interaction of the anti-atom. Our results, utilizing a 50-term explicitly correlated exponential ...


The Investigation Of The Chlorine Initiated Oxidation Of 2-Phenylethanol And Stability Of Superalkali Lithium Substituted Silyls., Adam Otten Dec 2018

The Investigation Of The Chlorine Initiated Oxidation Of 2-Phenylethanol And Stability Of Superalkali Lithium Substituted Silyls., Adam Otten

Master's Theses

This thesis investigates the combustion potential of 2-phenylethanol and the superalkali properties of small lithium substituted silicon compounds. All combustion experiments were performed at the Advanced Light Source of Lawrence Berkeley National Laboratory at the Chemical Dynamics Beamline 9.0.2. The chlorine initiated oxidation of 2PE was investigated at 298 and 550 K using a multiplex photoionization mass spectrometer, coupled with the tunable vacuum ultraviolet radiation. Reaction products were identified using kinetic time traces and photoionization spectra.

Additionally, the stability of small superalkali silicon-lithium compounds has also been investigated. All structures and energetics were calculated using the CBS-QB3 composite ...


The Formation And Dynamics Of Clouds In The Environment Of Active Galactic Nuclei, Timothy Waters Aug 2017

The Formation And Dynamics Of Clouds In The Environment Of Active Galactic Nuclei, Timothy Waters

UNLV Theses, Dissertations, Professional Papers, and Capstones

Active galactic nuclei (AGN) are among the most luminous objects in the universe and are known to be powered by accretion onto supermassive black holes in the centers of galaxies. AGN clouds are prominent components of successful models that attempt to unify the diversity of AGN. These clouds are often hypothesized to be the source of the broad and narrow line emission features seen in AGN spectra. Moreover, the high column densities of gas needed to account for broad absorption lines has been attributed to the same population of clouds, while the motion of AGN clouds has been invoked to ...


Time-Dependent Photoionization Of Gaseous Nebulae, Ehab Elsayed Elhoussieny Ahmed Jun 2017

Time-Dependent Photoionization Of Gaseous Nebulae, Ehab Elsayed Elhoussieny Ahmed

Dissertations

We study time-dependent photoionization of gaseous nebulae, i.e. the physical conditions and spectra of astronomical plasmas photoionized by a time-dependent source of ionizing radiation. Our study proceeds in two chief steps: First, we start with a simplified model of plasmas of pure H. Second, we develop a more realistic model of plasmas composed of a mixture of chemical elements. For the first step, we wrote a time-dependent photoionization code (TDP) that solves the coupled system of equations for ionization, energy balance, and radiation transfer in their full time-dependent forms For the second step, we developed a more realistic code ...


The Investigation And Characterization Of The Reaction Of 2-Methylfuran And 2-Methyl-3-Buten-2-Ol With O(3p) And The Photodissociation Of Xylyl Bromide Isomers, Yasmin Fathi May 2017

The Investigation And Characterization Of The Reaction Of 2-Methylfuran And 2-Methyl-3-Buten-2-Ol With O(3p) And The Photodissociation Of Xylyl Bromide Isomers, Yasmin Fathi

Master's Theses

This thesis has studied the oxidation behavior of different biofuels or additives, 2-methyl-3-buten-2-ol and 2-methylfuran, in combustion experiments at the Chemical Dynamics Beamline held at the Advanced Light Source of the Lawrence Berkley National Laboratory. The oxidation of these fuels were initiated through O(3P) and the combustion experiments were analyzed using a multiplexed chemical kinetics photoionization mass spectrometer with tunable synchrotron radiation. Products of the different reactions were identified using kinetic profiles and further characterized using the photoionization spectra. The amount of each species was calculated using branching fractions.

Additionally, the unimolecular dissociation of the xylyl bromide isomers ...


Characterization Of Etbe + Cl And Isooctane + Cl Combustion Products Using Synchrotron Photoionization, Rong Yao Aug 2016

Characterization Of Etbe + Cl And Isooctane + Cl Combustion Products Using Synchrotron Photoionization, Rong Yao

Master's Theses

The low temperature (298 – 700 K) oxidation characterizations of a series of fuel additives (ETBE and isooctane) were studied at advanced light source in Lawrence Berkley National lab, using a multiplexed chemical kinetics photoionization mass spectrometer with tunable synchrotron radiation. Using Cl atoms as initiators in presence of oxygen, photoionization data were collected. Data analysis was performed via characterization of the reaction species photoionization spectra and kinetic traces, from which the products and also the intermediates were identified. Relevant reaction dynamics on potential energy surfaces were calculated, reaction enthalpies of each individual step were presented using the CBS-QB3 composite model ...


An R-Matrix, Quantum Defect Theory Approach To The Photoionization Of Molecular Nitrogen, Gaetan L. Vangyseghem Aug 2016

An R-Matrix, Quantum Defect Theory Approach To The Photoionization Of Molecular Nitrogen, Gaetan L. Vangyseghem

Dissertations

No abstract provided.


Probing And Extracting The Structure Of Vibrating Sf₆ Molecules With Inner-Shell Photoelectrons, Ngoc-Ty Nguyen, R. R. Lucchese, C. D. Lin, Anh-Thu Le Jun 2016

Probing And Extracting The Structure Of Vibrating Sf₆ Molecules With Inner-Shell Photoelectrons, Ngoc-Ty Nguyen, R. R. Lucchese, C. D. Lin, Anh-Thu Le

Physics Faculty Research & Creative Works

We propose a scheme for probing the structure of vibrating molecules with photoelectrons generated from ultrashort soft-x-ray pulses. As an example we analyze below-100-eV photoelectrons liberated from the S(2p) orbital of vibrating SF₆ molecules to image very small structural changes of molecular vibration. In particular, photoionization cross sections and photoelectron angular distributions (PAD) at nonequilibrium geometries can be retrieved accurately with photoelectrons near the shape resonance at 13 eV. This is achieved with a pump-probe scheme, in which the symmetric stretch mode is first Raman excited predominantly by a relatively short laser pulse and then later probed at different ...


A Case For Chiral Contributions To Nondipole Effects In Photoionization Using Linearly Polarized Soft X-Rays, Kyle Patrick Bowen May 2016

A Case For Chiral Contributions To Nondipole Effects In Photoionization Using Linearly Polarized Soft X-Rays, Kyle Patrick Bowen

UNLV Theses, Dissertations, Professional Papers, and Capstones

Modelling angular distributions of photoelectrons requires making accurate approximations of both the incoming light and the behavior of bound electrons. The experimental determination of photoelectron angular distributions is crucial to the development of accurate theoretical models governing the light-matter interaction. To date, many models have relied upon the dipole approximation, which assumes a constant electric field as the source of ionization. Despite knowing that the dipole approximation would break down as photon energy increased, the precise limit was unclear. Over the past two decades, a strong case has been made that corrections to the dipole approximation are necessary for accurately ...


Photo-Induced Dissociation Dynamics Of Atmospherically Significant Criegee Intermediates, Hongwei Li Jan 2016

Photo-Induced Dissociation Dynamics Of Atmospherically Significant Criegee Intermediates, Hongwei Li

Publicly Accessible Penn Dissertations

Alkene ozonolysis, which proceeds through energized carbonyl oxide species also known as Criegee intermediates, is an important oxidation process for atmospheric alkenes and a significant source of hydroxyl (OH) radicals in the troposphere. Criegee intermediates (CH2OO, CH3CHOO, (CH3)2COO) are synthesized by the reaction of iodoalkyl radicals with molecular oxygen in a quartz capillary reactor, cooled in a free jet expansion, and characterized through ultraviolet (UV) and/or infrared (IR) induced dynamical studies. The dissociation dynamics of CH2I2 is investigated using velocity map imaging (VMI) to obtain the velocity distribution of the iodine atom products. The corresponding high internal excitation ...


Self-Consistent Modeling Of Photoionization And The Kerr Effect In Bulk Solids, Jeremy R. Gulley, Thomas E. Lanier Nov 2015

Self-Consistent Modeling Of Photoionization And The Kerr Effect In Bulk Solids, Jeremy R. Gulley, Thomas E. Lanier

Faculty Publications

In calculations of ultrafast laser-induced ionization the treatment of fundamental mechanisms such as photoionization and the Kerr effect are treated in isolation using monochromatic perturbative approaches. Such approaches are often questionable for pulses of ultrashort duration and multi-chromatic spectra. In this work we address this issue by solving the quantum optical Bloch equations in a 3D quasi-momentum space and show how to couple this model to ultrashort pulse propagation in dielectrics. This approach self-consistently couples a quantum calculation of the photoionization yield, the photoionization current, and the current from free-carriers with the traditional Kerr effect (self-focusing and self phase modulation ...


Optically Thin Broad-Line Clouds In Active Galactic Nuclei, Joseph C. Shields, Gary J. Ferland, Bradley M. Peterson Oct 2015

Optically Thin Broad-Line Clouds In Active Galactic Nuclei, Joseph C. Shields, Gary J. Ferland, Bradley M. Peterson

Gary J. Ferland

The broad-line region (BLR) in Seyfert galaxy nuclei exhibits correlated variations in continuum and emission-line luminosity that are qualitatively consistent with photoionization of ionization-bounded (optically thick) clouds. However, evidence is growing that a nonnegligible fraction of the BLR cloud population is optically thin to the Lyman continuum and fully ionized in hydrogen. We consider the implications of this nebular component for observed line emission and find that inclusion of thin clouds in photoionization calculations can resolve several outstanding puzzles of Seyfert variability, notably the behavior of the C IV λ1549/Lyα ratio as a function of continuum luminosity. A similar ...


The Narrow-Line Region Of High-Luminosity Active Galactic Nuclei, Beverley J. Wills, H. Netzer, M. S. Brotherton, Mingsheng Han, D. Wills, J. A. Baldwin, Gary J. Ferland, I. W. A. Browne Oct 2015

The Narrow-Line Region Of High-Luminosity Active Galactic Nuclei, Beverley J. Wills, H. Netzer, M. S. Brotherton, Mingsheng Han, D. Wills, J. A. Baldwin, Gary J. Ferland, I. W. A. Browne

Gary J. Ferland

We have made high signal-to-noise spectroscopic observations of seven radio-loud quasars with the Faint Object Spectrograph on the Hubble Space Telescope and from the ground at McDonald Observatory and at Kitt Peak National Observatory. The resolution is 300-400 km s-1 over the wavelength range 1000-8500 Å, enabling us to separate the broad and narrow components of the emission lines. This is the first study of the optical and UV narrow lines in such high-luminosity active galactic nuclei (AGNs). The most important and striking observational result is the relative weakness of the narrow ultraviolet lines, assuming that they have the same ...


Revisiting Ulysses Observations Of Interstellar Helium, Brian E. Wood, Hans-Reinhard Müller, Manfred Witte Mar 2015

Revisiting Ulysses Observations Of Interstellar Helium, Brian E. Wood, Hans-Reinhard Müller, Manfred Witte

Open Dartmouth: Peer-reviewed articles by Dartmouth faculty

We report the results of a comprehensive reanalysis of Ulysses observations of interstellar He atoms flowing through the solar system, the goal being to reassess the interstellar He flow vector and to search for evidence of variability in this vector. We find no evidence that the He beam seen by Ulysses changes at all from 1994-2007. The direction of flow changes by no more than ~03 and the speed by no more than ~0.3 km s–1. A global fit to all acceptable He beam maps from 1994-2007 yields the following He flow parameters: V ISM = 26.08 ± 0 ...


Benchmarking Accurate Spectral Phase Retrieval Of Single Attosecond Pulses, Hui Wei, Anh-Thu Le, Toru Morishita, Chao Yu, C. D. Lin Feb 2015

Benchmarking Accurate Spectral Phase Retrieval Of Single Attosecond Pulses, Hui Wei, Anh-Thu Le, Toru Morishita, Chao Yu, C. D. Lin

Physics Faculty Research & Creative Works

A single extreme-ultraviolet (XUV) attosecond pulse or pulse train in the time domain is fully characterized if its spectral amplitude and phase are both determined. The spectral amplitude can be easily obtained from photoionization of simple atoms where accurate photoionization cross sections have been measured from, e.g., synchrotron radiations. To determine the spectral phase, at present the standard method is to carry out XUV photoionization in the presence of a dressing infrared (IR) laser. In this work, we examine the accuracy of current phase retrieval methods (PROOF and iPROOF) where the dressing IR is relatively weak such that photoelectron ...


Electron- And Photon-Impact Ionization Of Furfural, D. B. Jones, E. Ali, K. L. Nixon, P. Limão-Vieira, M.-J. Hubin-Franskin, J. Delwiche, C. G. Ning, J. Colgan, Andrew J. Murray, Don H. Madison, M .J. Brunger Jan 2015

Electron- And Photon-Impact Ionization Of Furfural, D. B. Jones, E. Ali, K. L. Nixon, P. Limão-Vieira, M.-J. Hubin-Franskin, J. Delwiche, C. G. Ning, J. Colgan, Andrew J. Murray, Don H. Madison, M .J. Brunger

Physics Faculty Research & Creative Works

The He(i) photoelectron spectrum of furfural has been investigated, with its vibrational structure assigned for the first time. The ground and excited ionized states are assigned through ab initio calculations performed at the outer-valence Green's function level. Triple differential cross sections (TDCSs) for electron-impact ionization of the unresolved combination of the 4a" + 21a' highest and next-highest occupied molecular orbitals have also been obtained. Experimental TDCSs are recorded in a combination of asymmetric coplanar and doubly symmetric coplanar kinematics. The experimental TDCSs are compared to theoretical calculations, obtained within a molecular 3-body distorted wave framework that employed either an ...


Spectroscopy And Photo-Induced Chemistry Of Atmospherically Significant Criegee Intermediates And Hydroxyl Radicals, Fang Liu Jan 2015

Spectroscopy And Photo-Induced Chemistry Of Atmospherically Significant Criegee Intermediates And Hydroxyl Radicals, Fang Liu

Publicly Accessible Penn Dissertations

Criegee intermediates, carbonyl oxide species important in alkene ozonolysis reactions in the atmosphere, have eluded characterization until very recently. Four prototypical Criegee intermediates, CH2OO, CH3CHOO, (CH3)2COO and CH3CH2CHOO, were generated by photolysis of gem-diiodo compounds and subsequent reaction with oxygen in a quartz capillary tube reactor prior to free jet expansion. The Criegee intermediates were ionized using fixed-frequency vacuum ultraviolet (VUV) radiation and detected in a time-of-flight mass spectrometer. Ultraviolet (UV) excitation of the Criegee intermediates on very strong pi*-pi transitions localized on the COO group induced significant depletion of the ion signals near the peak of broad ...


Electron-Ion Equilibrium And Shock Precursors In The Northeast Limb Of The Cygnus Loop, Amber A. Medina, John C. Raymond, Richard J. Edgar, Nelson Caldwell, Robert A. Fesen, Dan Milisavljevic Jul 2014

Electron-Ion Equilibrium And Shock Precursors In The Northeast Limb Of The Cygnus Loop, Amber A. Medina, John C. Raymond, Richard J. Edgar, Nelson Caldwell, Robert A. Fesen, Dan Milisavljevic

Open Dartmouth: Peer-reviewed articles by Dartmouth faculty

We present an observational study using high-resolution echelle spectroscopy of collisionless shocks in the Cygnus Loop supernova remnant. Measured Hα line profiles constrain pre-shock heating processes, shock speeds, and electron-ion equilibration (Te /Ti ). The shocks produce faint Hα emission line profiles, which are characterized by narrow and broad components. The narrow component is representative of the pre-shock conditions, while the broad component is produced after charge transfer between neutrals entering the shock and protons in the post-shock gas, thus reflecting the properties of the post-shock gas. We observe a diffuse Hα region extending about 25 ahead of the ...


Interaction Between The Broad-Lined Type Ic Supernova 2012ap And Carriers Of Diffuse Interstellar Bands, Dan Milisavljevic, Raffaella Margutti, Kyle N. Crabtree, Jonathan B. Foster, Alicia M. Soderberg, Robert A. Fesen, Jerod T. Parrent Feb 2014

Interaction Between The Broad-Lined Type Ic Supernova 2012ap And Carriers Of Diffuse Interstellar Bands, Dan Milisavljevic, Raffaella Margutti, Kyle N. Crabtree, Jonathan B. Foster, Alicia M. Soderberg, Robert A. Fesen, Jerod T. Parrent

Open Dartmouth: Peer-reviewed articles by Dartmouth faculty

Diffuse interstellar bands (DIBs) are absorption features observed in optical and near-infrared spectra that are thought to be associated with carbon-rich polyatomic molecules in interstellar gas. However, because the central wavelengths of these bands do not correspond to electronic transitions of any known atomic or molecular species, their nature has remained uncertain since their discovery almost a century ago. Here we report on unusually strong DIBs in optical spectra of the broad-lined Type Ic supernova SN 2012ap that exhibit changes in equivalent width over short ( 30 days) timescales. The 4428 Å and 6283 Å DIB features get weaker with time ...


On The Production Of The Positive Antihydrogen Ion H̄+ Via Radiative Attachment, Chris M. Keating, M. Charlton, Jack C. Straton Jan 2014

On The Production Of The Positive Antihydrogen Ion H̄+ Via Radiative Attachment, Chris M. Keating, M. Charlton, Jack C. Straton

Physics Faculty Publications and Presentations

We provide an estimate of the cross section for the radiative attachment of a second positron into the state of the ion using Ohmura and Ohmura's (1960 Phys. Rev. 118 154) effective range theory and the principle of detailed balance. The ion can potentially be created using interactions of positrons with trapped antihydrogen, and our analysis includes a discussion in which estimates of production rates are given. Motivations to produce include its potential use as an intermediary to cool antihydrogen to ultra-cold (sub-mK) temperatures for a variety of studies, including spectroscopy and probing the gravitational interaction of the anti-atom.


High-Order-Harmonic Generation From Molecular Isomers With Midinfrared Intense Laser Pulses, Anh-Thu Le, R. R. Lucchese, C. D. Lin Aug 2013

High-Order-Harmonic Generation From Molecular Isomers With Midinfrared Intense Laser Pulses, Anh-Thu Le, R. R. Lucchese, C. D. Lin

Physics Faculty Research & Creative Works

We present theoretical calculations of high-order-harmonic generation (HHG) from stereoisomers of 1,2-dichloroethylene (C₂H₂Cl₂) and 2-butene (C₄H₈) based on the quantitative rescattering theory. Our results show that the HHG spectra from these cis and trans isomers with intense midinfrared laser pulses are clearly distinguishable, even when the molecules are randomly oriented, in good agreement with the recent experiments by Wonget al. [Phys. Rev. A 84, 051403(R) (2011)]. We found that the angle-averaged tunneling ionization yields and photoionization cross sections from the cis and trans isomers for both molecules are nearly identical. The origin of the differences in HHG spectra ...


Isomer-Specific Product Detection Of Cn Radical Reactions With Ethene And Propene By Tunable Vuv Photoionization Mass Spectrometry, Adam Trevitt, Fabien Goulay, Giovanni Meloni, David Osborn, Craig Taatjes, Stephen Leone Jul 2013

Isomer-Specific Product Detection Of Cn Radical Reactions With Ethene And Propene By Tunable Vuv Photoionization Mass Spectrometry, Adam Trevitt, Fabien Goulay, Giovanni Meloni, David Osborn, Craig Taatjes, Stephen Leone

Adam Trevitt

No abstract provided.


Branching Fractions Of The Cn + C3h6 Reaction Using Synchrotron Photoionization Mass Spectrometry: Evidence For The 3-Cyanopropene Product, Adam Trevitt, Talitha Selby, Craig Taatjes, Satchin Soorkia, J Savee, D L Osborn, S R Leone Jul 2013

Branching Fractions Of The Cn + C3h6 Reaction Using Synchrotron Photoionization Mass Spectrometry: Evidence For The 3-Cyanopropene Product, Adam Trevitt, Talitha Selby, Craig Taatjes, Satchin Soorkia, J Savee, D L Osborn, S R Leone

Adam Trevitt

The gas-phase CN + propene reaction is investigated using synchrotron photoionization mass spectrometry (SPIMS) over the 9.8 - 11.5 eV photon energy range. Experiments are conducted at room temperature in 4 Torr of He buffer gas. The CN + propene addition reaction produces two distinct product mass channels, C3H3N and C4H5N, corresponding to CH3 and H elimination, respectively. The CH3 and H elimination channels are measured to have branching fractions of 0.59 + 0.15 and 0.41 + 0.10, respectively. The absolute photoionization cross sections between 9.8 and 11.5 eV are measured for the three considered H-elimination coproducts ...


Atmospheric Pressure He-Air Plasma Jet: Breakdown Process And Propagation Phenomenon, Asma Begum, Mounir Laroussi, Mohammad Rasel Pervez Jun 2013

Atmospheric Pressure He-Air Plasma Jet: Breakdown Process And Propagation Phenomenon, Asma Begum, Mounir Laroussi, Mohammad Rasel Pervez

Electrical & Computer Engineering Faculty Publications

In this paper He-discharge (plasma jet/bullet) in atmospheric pressure air and its progression phenomenon has been studied experimentally using ICCD camera, optical emission spectroscopy (OES) and calibrated dielectric probe measurements. The repetitive nanosecond pulse has applied to a plasma pencil to generate discharge in the helium gas channel. The discharge propagation speed was measured from the ICCD images. The axial electric field distribution in the plasma jet is inferred from the optical emission spectroscopic data and from the probe measurement. The correlation between the jet velocities, jet length with the pulse duration is established. It shows that the plasma ...


Photoionization Mass Spectrometry And Photoelectron-Photoion Coincidence (Pepico) Spectroscopy Studies Of Select Biofuel Molecules, Joseph G. Czekner May 2013

Photoionization Mass Spectrometry And Photoelectron-Photoion Coincidence (Pepico) Spectroscopy Studies Of Select Biofuel Molecules, Joseph G. Czekner

Master's Theses

This thesis is the culmination of numerous experiments, performed on two different continents, investigating the spectroscopic and thermodynamic properties of several biofuels and fuel additives. It will start with an introduction about the motivation behind these experiments. The second chapter will outline the experimental details of the apparatus at the Advanced Light Source (ALS) in Berkeley, CA, followed by the Swiss Light Source (SLS) in Villigen, Switzerland. Third, the theoretical concepts and data analysis methods will be discussed in detail.

Chapter 4 will be the start of the newly obtained data. It presents some photoionization mass spectrometry studies on γ-valerolactone ...


Seeing Through A Cloudy Glass: Putting Limits On Planetary Nebulae Abundances Using Photoionization Modeling., Peter R. Sullivan, Ravi Sankrit Jan 2013

Seeing Through A Cloudy Glass: Putting Limits On Planetary Nebulae Abundances Using Photoionization Modeling., Peter R. Sullivan, Ravi Sankrit

STAR (STEM Teacher and Researcher) Presentations

Planetary nebulae (PNe) form around low to intermediate mass stars transitioning from the giant branch to white dwarf phase. The outer layer of the star is ejected during the transition and this gas, ionized by the central star, emits a line-spectrum. This spectrum traces the chemical abundances that were characteristic of the interstellar medium in which the star formed (e.g. oxygen) as well as of the elements created by these progenitor stars (e.g. nitrogen) aiding our understanding of chemical evolution of galaxies. In this project, we use modeling of the emission lines of PNe to determine the accuracy ...


Radiative Double Electron Capture In Collisions Of Fully-Stripped Fluorine Ions With Thin Carbon Foils, Tamer Mohammad Samy Elkafrawy Dec 2012

Radiative Double Electron Capture In Collisions Of Fully-Stripped Fluorine Ions With Thin Carbon Foils, Tamer Mohammad Samy Elkafrawy

Dissertations

Radiative double electron capture (RDEC) is a one-step process in ion-atom collisions occurring when two target electrons are captured to a bound state of the projectile simultaneously with the emission of a single photon. The emitted photon has approximately double the energy of the photon emitted due to radiative electron capture (REC), which occurs when a target electron is captured to a projectile bound state with simultaneous emission of a photon. REC and RDEC can be treated as timereversed photoionization (PI) and double photoionization (DPI), respectively, if loosely-bound target electrons are captured. This concept can be formulated with the principle ...


K-Shell X-Ray Spectroscopy Of Atomic Nitrogen, M. M. Sant'anna, Gunnar Ohrwall, Wayne C. Stolte, Alfred S. Schlachter, Dennis W. Lindle, B. M. Mclaughlin Mar 2012

K-Shell X-Ray Spectroscopy Of Atomic Nitrogen, M. M. Sant'anna, Gunnar Ohrwall, Wayne C. Stolte, Alfred S. Schlachter, Dennis W. Lindle, B. M. Mclaughlin

Chemistry and Biochemistry Faculty Publications

Absolute K-shell photoionization cross sections for atomic nitrogen have been obtained from both experiment and state-of-the-art theoretical techniques. Because of the difficulty of creating a target of neutral atomic nitrogen, no high-resolution K-edge spectroscopy measurements have been reported for this important atom. Interplay between theory and experiment enabled identification and characterization of the strong 1s → np resonance features throughout the threshold region. An experimental value of 409.64 ± 0.02 eV was determined for the K-shell binding energy.


Novel Nonresonant And Resonant Mechanisms Leading To The Breakdown Of The Franck-Condon Approximation In Photoionization, David Adam Hardy Jan 2012

Novel Nonresonant And Resonant Mechanisms Leading To The Breakdown Of The Franck-Condon Approximation In Photoionization, David Adam Hardy

LSU Doctoral Dissertations

This thesis attempts to answer the question of how electrons interact with a molecular framework prior to and during emission through photoionization. These studies interrogate several behaviors of allowed and forbidden photoelectron transitions such as shape resonances, non-resonant intrachannel vibronic coupling as a result of Cooper minima, and chemically-induced nonresonant coupling, all of which provide new insights into correlations between the electronic and molecular degrees of freedom. Research presented in this thesis utilizes high-resolution photoelectron spectroscopy, and undulator-based synchrotron radiation at the Advanced Light Source, a synchrotron radiation source in Berkeley, California. Data are collected from near threshold to several ...


Photoionization Of The Potassium Isoelectronic Sequence: Ca+ And Transition Metal Ions, Ayao M. Sossah Dec 2010

Photoionization Of The Potassium Isoelectronic Sequence: Ca+ And Transition Metal Ions, Ayao M. Sossah

Physics and Astronomy Dissertations

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 ...