Electron collisions with cesium atoms -- benchmark calculations and application to modeling an excimer-pumped \hbox{alkali} laser

The {\it B}-spline {\it R}-matrix (BSR) with pseudo\-states method~[1] was employed to describe electron collisions with cesium atoms. Over 300 states were kept in the close-coupling expansion, including a large number of pseudo\-states 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, excitation, and ionization will be presented for incident energies up to 200~eV and compared to results from previous calculations~[2,3] and available experimental data. The results of our calculations were used to model plasma formation in the excimer-pumped alkali laser, XPAL, operating on the Cs$\,\rm (6^2P_{3/2,1/2} \to (6^2S_{1/2})$ (852$\,$nm and 894$\,$nm) transitions. At sufficiently high operating temperature, pump power, and repetition rate, plasma formation in excess of $\rm 10^{14}-10^{15}\,cm^{-3}$ occurs. This may reduce laser output power by electron collisional mixing of the upper and lower laser levels.\\[4pt] [1]~O.~Zatsarinny and K.~Bartschat, J.~Phys.~B~{\bf 46} (2013) 112001.\\[0pt] [2]~K.~Bartschat and Y.~Fang, Phys.~Rev.~A {\bf 62} (2000) 052719.\\[0pt] [3]~O.~Zatsarinny and K.~Bartschat, Phys.~Rev.~A {\bf 77} (2008) 062701.