Numerical study of Kα emission from partially ionized chlorine

Population kinetics and spectral synthesis codes have been developed to analyze Kα emission from partially ionized chlorine in hydrocarbon plasmas irradiated with high-intensity ultra-short laser pulses. The population kinetics processes are calculated using a bi-Maxwellian electron temperature distribution composed of fast and cold electrons. The fast electrons dominantly contribute to ionize the K-shell bound electrons. i.e., inner-shell ionization, while the cold electrons produce ionization from the outer-shell electrons. The resultant Kα emission provides a distinct spectral signature for each charge state. Also included in the calculation are the opacity effects in the framework of an escape probability method. It is shown that the Kα emission is saturated at a plasma thickness of more than a few microns. Further, we find that unresolved satellite lines overlap significantly with the corresponding parent Kα lines of the next charge state, and make a large contribution to composite spectrum. Finally, time-dependent properties of the Kα emission are also discussed briefly.