Ionization dynamics and radiative behavior of a betatron driven gold atom

Abstract

The study of inner-shell transitions induced by an intense (>1019 W/cm2) ultrashort (∼5 fs) x-ray pulse provides a challenging opportunity to investigate the behavior and dynamics of hollow atoms and to explore the feasibility of creating population inversions in some of the inner-shell states that may lead to a variety of amplifications and gains in the x-ray regime. In this paper, we investigate the interaction through inner-shell photoionizations of a spectrally broad femtosecond pulse of betatron x-ray radiation incident on a gold atom. The level populations of Pt-like Au and Ir-like Au are described by non-(local thermodynamic equilibrium) inner-shell dynamics and compared and contrasted with the level populations created by a "single" frequency x-ray laser pulse. Gain coefficients for a variety of transitions are calculated. It is found that long wavelength x-rays must be filtered from the betatron spectrum before any population inversions can be generated.

Preface to Special Topic Section: Radiation from High Energy Density Plasmas

“…The potential for laser driven inversions in gold arise if one considers pumping the target foil with a high intensity, x-ray laser. For example, Davis et al 20 present a theoretical study of inner shell photo-ionization subject to a high intensity ($10 19 W/cm 2 ) pulse of x-rays. The non-LTE ionization kinetics and population inversions in Au ions resulting from a broadband spectrum of betatron x-ray radiation are contrasted with a single frequency x-ray laser pulse.…”