The hollow atom formation and de-excitation simulation package

Abstract

Hollow atoms (HA) are an exotic species of atoms: They are formed when a highly charged ion approaches a surface and resonantly captures electrons in states with principal quantum number nc roughly equal to its incident charge state q;n ~ nc [1]. The HAs will subsequently de-excite, typically via (auto-ionizing) Auger as weil as radiative pathways. We present a simulation package where the capture of the electrons is described self-consistently using the classical-over-the-barrier model. The subsequent de-excitation is modelled using rate equations and a Monte-Carlo approach [l,2]. In addition, our code allows to obtain the spectra of the emitted photons as weil as electrons resulting from these de-excitation processes. However, the dynamics of the formation and de-excitation processes strongly depend on accurate rates for these transitions. Previously, due to constraints in both computational power as weil as general availability of experimental rate data, simple fit-formulas were used. To improve these inputs we use a combination of experimentally available data [3] as weil as the Flexible Atomic Code (FAC) package [4] are used to find an improved and more general fit for future simulations. The left figure shows an (updated) fit for radiative rates (solid lines) obtained from experimental data (dots) [3]. The right figure shows preliminary data for the auto-ionization rates, computed using the FAC code package [4].