Ionization and excitation of atomic and molecular gases exposed to intense extreme ultraviolet radiation: theory and experiment

Abstract: Photoionization in gases exposed to intense short-wavelength radiation plays an important role in astrophysics, planetology, fusion research, and the development of 4th generation short-wavelength sources. For several decades, photoionization of gases has been studied using sources of ionizing electromagnetic radiation with low peak brightness (e.g., Henke's tubes, synchrotron radiation sources, etc.). The recent advent of extreme ultraviolet (XUV) and soft X-ray (SXR) lasers made it possible to study photoionization of isolated atoms and molecules, as well as collective processes (e.g., instabilities, recombination, etc.) in the photoionized gas, with high-amplitude, ultra-high-frequency electromagnetic radiation. The project deals both with theoretical and experimental investigations of the ionization and excitation dynamics in atomic and molecular gases exposed to nanosecond and femtosecond pulses of radiation with a wavelength of 50 nm and intensities of 109-1016 W/cm2 delivered by a capillary discharge laser and a free-electron laser, respectively.