Analysis of low energy X-ray and excitation spectra of Ba 35+

Abstract

We present a theoretical analysis of the low energy X-ray spectra of the Ba³⁵⁺ + e ^- system, in the energy region below 2 keV, for comparison with future experiments. In a recent study carried out at the National Institute of Standards and Technology, scandium-like Ba³⁵⁺ ions were created, trapped and excited using an Electron Beam Ion Trap and an electron beam with kinetic energy of 2.35 keV. The theory agrees well with experiment for X-ray energies in the region 2–5 keV. The experiment also gives evidence suggestive of a large cross section for X-ray production in the region below 2.0 keV. We include the contribution to the X-ray spectra of collisional excitation followed by fluorescence decay, radiative cascade processes, M-shell dielectronic recombination, Bremsstrahlung, and a new off-shell, quasi-resonant continuum dielectronic recombination process. We find that excitation fluorescence is the dominant process, with smaller contributions from the other radiative cascade processes as well as a continuous Bremsstrahlung background.