Non-Equilibrium Plasma Dynamics Modeling of Xenon Clusters Irradiated by an Intense Laser Pulse

Population inversions have been experimentally observed when small xenon clusters of 5-20 atoms are irradiated by $\sim $230 fs high intensity laser of 10$^{19}$ W/cm$^{2}$ and wavelength of 248 nm [1]. Consequently, a plasma channel $\sim$1.5-2 cm in length and $\sim$1.5--2 $\mu$m in diameter is formed which produces amplified x-ray emissions with gains $\sim$20-60 for wavelengths in the range 2.71-3 {\AA}. It has been conjectured [2], that population inversions in laser generated xenon plasmas may be efficiently created within M-shell ionization stages by photo- or collisional-ionization of 2s and 2p inner shell electrons. In this study we focus our attention on the influence of non-Maxwellian electron energy distributions on the collisional dynamics by which hollow atoms are generated in different ionization stages of xenon. These distributions are calculated from a relativistic molecular dynamics model. \\[4pt] [1] A. B. Borisov, \textit{et al.}, J. Phys. B \textbf{40}, F307 (2007). \\[0pt] [2] W. A. Schroeder, \textit{et al}., J. Phys. B \textbf{34}, 297 (2001).