Hot-electron influence on L-shell line intensities of Kr multicharged ions produced in clusters irradiated by femtosecond laser pulses

Abstract

Summary form only given, as follows. The modeling of L-shell x-ray spectra from Kr clusters in laser plasmas is presented. Different types of nozzles create clusters composed of as many as (2-20) /spl times/ 10/sup 6/ Kr atoms, which are then irradiated by a high-intensity Ti:Sa 60-500 fs laser pulse. High-resolution (up to /spl lambda///spl Delta//spl lambda/ = 4000) L-spectra of Kr were obtained using X-ray Focusing Spectrometers with Spatial Resolution (FSSR). The spectrometers have been oriented to obtain spatial resolution of around 30-80 /spl mu/m in the direction perpendicular to laser propagation. A detailed time-dependent collisional-radiative model has been developed to diagnose the electron density, ionization balance, and electron distribution function of the plasmas both before and after the femtosecond pulse. The kinetic model and its application to laser plasmas from different nozzles are discussed in detail. Modeling was also performed on experimental spectra obtained from nanosecond laser interaction with Kr clusters. It is shown that the n=4 L-shell nanosecond laser plasma spectra can be adequately described by a single electron density and temperature, while similar spectra from femtosecond laser experiments require more sophisticated modeling with inclusion of hot electrons.