Strong multiple-capture effect in slow Ar$^{17+}$-Ar collisions: a quantum mechanical analysis*

A recent X-ray spectroscopy experiment on 255 keV Ar$^{17+}$-Ar collisions provided evidence for strong multiple-electron capture [1]. We have coupled a quantum-mechanical independent-electron model calculation for the collision dynamics with (semi-) phenomenological Auger and radiative cascade models to test this finding. The capture calculations are performed using the basis generator method and include single-particle states on the projectile up to the 10$^{\rm th}$ shell. The cross sections obtained for shell-specific multiple capture are fed into an Auger decay scheme in order to obtain $n$-specific cross sections for {\it apparent} single (and double) capture that together with the {\it actual} single capture cross sections are then fed into a radiative cascade code. This yields X-ray emission intensities that can be compared with the experimental data of [1]. Good agreement is found for the Lyman series from $n=3$ to $n=7$ if the multiple-capture contributions are included, whereas calculations that ignore them are in stark conflict with the measurements [2].\\[4pt] [1] M. Trassinelli {\it et al.}, J. Phys. B \textbf{45}, 085202 (2012);\\[0pt] [2] A. Salehzadeh and T. Kirchner, J. Phys. B \textbf{46}, 025201 (2013).