Two-photon ionization of an inner shell electron of the Cl atom

Boltzmann electron kinetic simulations are performed to study the time development of the electron energy distribution function (EEDF) in plasma resulting from neon gas subject to a 40 fs x-ray free electron laser radiation source. The simulations are performed without any assumptions of electron temperature. The distributions are calculated as a function of time through 40 fs using Boltzmann kinetics, including the appropriate processes that alter state populations and electron energy. The calculations are also extended into the picosecond regime, after the laser pulse, to track the thermalization of free electrons. Results are presented that predict the evolution of the charge-state distribution, effective temperature, the photon spectrum, as well as the EEDF.

Section: Methodsmentioning

confidence: 99%

Time-dependent calculations of electron energy distribution functions for neon gas in the presence of intense XFEL radiation

Abdallah¹,

Colgan²,

Rohringer³

2013

“…The CATS code [15], which is an adaptation of Cowan's atomic structure codes [16], was used to calculate wavefunctions, energy levels, oscillator strengths and planewave Born (PWB) collision strengths within the configurationaverage approximation. Electron-impact ionization, photoionization and auto-ionization cross sections were calculated using the multi-purpose ionization GIPPER code [17,18]. The latter two processes were calculated explicitly with distorted-wave continuum functions while the electronimpact ionization calculations used scaled hydrogenic cross sections that were designed to reproduce distorted-wave calculations.…”

Section: Theorymentioning

confidence: 99%

Time-dependent calculations of electron energy distribution functions for cold argon gas in the presence of intense black-body radiation

Abdallah¹,

Colgan²

2012

Boltzmann electron kinetic simulations are performed to study the time development of the electron energy distribution in a plasma that results from a cold argon gas subject to a black-body radiation source (100-300 eV). The study provides insight into the role of ionized electrons on the kinetics during a period of irradiation. The simulations are performed without any assumptions of electron temperature. The distributions are calculated as a function of time through 1 ps using Boltzmann kinetics, including the appropriate processes that alter state populations and electron energy. The processes included in the electron and atomic kinetics are collisional excitation/de-excitation, photo-excitation/decay, photoionization/radiative-recombination, collisional ionization, and auto-ionization/di-electronic capture. In addition, terms are included in the electron kinetics to account for electron-electron interactions and for free-free radiation absorption and emission. Results are presented that follow the evolution of the ionization state effective temperature as well as the electron energy distribution function (EEDF). The role of inelastic electron collisions, photo-ionization, auto-ionization, resonant radiative excitation, and electron-electron interactions are discussed.

“…By comparison with distorted wave calculations, scaled hydrogenic cross sections (Clark et al 1991b) were found to be sufficently accurate for ionization out of other levels. Photo-ionization cross sections from all levels in each ion stage were calculated (Abdallah et al 1995) using the distorted continuum functions. Auto-ionization rates for the doubly excited states of neutral helium were also calculated for the inclusion of auto-ionization and dielectronic capture.…”

Section: Computational Modelmentioning

confidence: 99%

Time-dependent kinetics model for a helium discharge plasma

Abdallah

Palmer

Gekelman

et al. 1999

Measurements of electron density and electron temperature at various times during a cathode discharge in helium have been recorded with a Langmuir probe in the UCLA large plasma device. The measured electron temperatures were then used in a time-dependent collisionalradiative model to propagate the electron density as a function of time for plasma conditions corresponding to population densities far from equilibrium. The initial gas density was extracted from pressure measurements and used in the calculations so there were no adjustable parameters in the model. The calculated and measured densities are in good agreement for three different radial positions in the plasma. The results show that the plasma formation becomes dominated by bulk thermal electrons early in the discharge. The detailed model is compared with several simplified models to study the role of metastable levels and excited states in the plasma kinetics. The relative importance of the various atomic processes in the calculation of plasma formation is also discussed.