Intense ultrashort laser-Xe cluster interaction

The last several years have witnessed an explosion of activity involving the interaction of clusters with intense ultrashort pulse lasers. The interest in laser-cluster interaction has not been only of academic interest, but also because of the wide variety of potential applications. Clusters can be used as a compact source of X-rays, incoherent as well as coherent radiation, and fast ions capable of driving a fusion reaction in deuterium plasma. Some of the applications include EUV lithography, EUV and X-ray microscopy, X-ray tomography and a variety of applications in biology and material sciences. In this talk a model of laser-cluster interaction dynamics is presented that describes the process of amplification from the incident laser pulse to the final gain calculations. The focus of this research is on the feasibility of creating population inversions and gain in some of the inner shell hole state transitions in highly ionized Xe. The model couples a molecular dynamics treatment of the explosively-driven cluster expansion to a comprehensive multiphoton-radiative ionization model including single- and double-hole state production within the Co-and Fe-like ionization stages of Xe. The hole state dynamics is self-consistently coupled to the valence-state collisional-radiative dynamics of the Ni-, Co-, and Fe-like ionization stages of xenon. In addition, the model includes tunneling ionization rates that confirm the initial condition assumption that Ni-like ground states are created almost instantaneously, the creation of which is needed to support the interpretations of the measured x-ray data. With the use of tunneling ionization rates, all of the N-shell, n=4 electrons are striped from a xenon atom in less than a femtosecond at laser intensities larger than 1019W/cm2. Thus, our calculations do not support the initial experimental data interpretations in which the measured gains have been associated with double holes in more highly ionized stages of xenon (Xe32+, Xe34+, Xe35+, and Xe37+).