Electron collisions with cesium atoms—benchmark calculations and application to modeling an excimer-pumped alkali laser

Abstract

The B-spline R-matrix (BSR) with pseudostates method is employed to describe electron collisions with cesium atoms. Over 300 states are kept in the close-coupling expansion, including a large number of pseudostates to model the effect of the Rydberg spectrum and, most importantly, the ionization continuum on the results for transitions between the discrete physical states of interest. Predictions for elastic scattering, momentum transfer, excitation and ionization are presented for incident energies up to 200 eV and compared with results from previous calculations and available experimental data. In a second step, the results are used to model plasma formation in an excimer-pumped alkali laser operating on the Cs (6 2 P 3/2,1/2 → 6 2 S 1/2) (852 nm and 894 nm) transitions. At sufficiently high operating temperature of a Cs-Ar containing quartz cell, pump power, and repetition rate, plasma formation in excess of 10 14-10 15 cm −3 occurs. This may reduce laser output power by electron collisional mixing of the upper and lower laser levels.

Electron collisions with atoms, ions, molecules, and surfaces: Fundamental science empowering advances in technology

“…Optical pumping of Cs vapor and possible plasma formation was discussed in detail in a recent paper (37). It is an excellent example of a mutually beneficial collaboration between data producers and data users.…”

“…This plasma ultimately reduces the laser power by depletion of the ground state through ionization and by electron-collision mixing of the laser levels (37).…”

Implementing and constraining higher fidelity kinetics for DPAL models

“…For the usual extent of population inversion, electrons experience net energy gain from collisions with potassium. Inversion between D1 and D2 even gives a noticeable contribution, a fact previously recognized by Markosyan and Kushner [5], and Zatsarinny et al [4]. Even if all the alkali were ionized, energy transfer via elastic collisions with helium still dominate electron-electron energy transfer.…”

“…Wallerestein et al [3] considered an even broader set of processes involving the bound electrons, and emphasized building intuition for the hierarchy of processes based on their timescales, and likely availability of reactants. However, Zatsarinny et al [4], and Markosyan et al [5,6], did consider a non-Maxwell-Boltzmann (non-MB) electron energy distribution through the use of finely-grained lookup tables [7]. We also relax the Maxwell-Boltzmann assumption, but model, and evolve the electron distribution a bit differently, and focus on experimental comparisons.…”

Microwave-assisted modulation of light emission intensity in alkali-pyrotechnic plumes

“…Crosssections for equilibrium products are obtained from the LXCat database for N 2 [32] , CO [33] , and Mg [34] , which are used to approximate non-alkali combustion products. Alkali cross sections for elastic, excitation, and ionization are obtained for sodium, potassium, and cesium [35][36][37] . The resulting rates are computed as functions of the reduced root-mean square (RMS) electric field ( E/ n 0 , units of Td) and fitted to quadratic and logarithmic functions of electric field magnitude E(s ) once total number density inside the plume n 0 is known.…”