Stabilized double-electron capture in Ne10+-He collisions: Velocity dependence of Rydberg-electron n,l distributions.

Abstract

The distribution over the n states populated by double-electron capture in ${\mathrm{Ne}}^{10+}$-He collisions has been determined in the energy range of 0.9\char21{}9 keV/u by analyzing the radiative decays of projectile Rydberg transitions. It has been found to be in fair agreement with predictions of the autotransfer-to-Rydberg-states model of Roncin et al. [J. Phys. B 26, 4181 (1993)]. Double-capture stabilization ratio ${\mathit{R}}_{\mathit{S}}$, defined as the ratio of true double capture ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{TDC}}$ to the sum of ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{TDC}}$ and autoionizing double capture ${\mathrm{\ensuremath{\sigma}}}_{\mathrm{ADC}}$, has been studied at various energies. A slight enhancement of ${\mathit{R}}_{\mathit{S}}$ (35\char21{}50 %) and an increase by a factor of 5 of the cross sections for emission of optical transitions from (3,n) Rydberg states have been found as the projectile velocity decreases from 0.6 to 0.19 a.u. We propose a tentative explanation following a model of postcollisional satellization of Rydberg electrons.