Evidence for resonant double electron capture and single excitation in Ge³¹⁺ → Ne collisions

Abstract

Evidence for resonant two-electron capture and excitation, i.e. the time-reversed double-Auger process with radiative stabilization, was found in collisions between hydrogenic ₃₂Ge³¹⁺ projectiles and Ne gas atoms. The multiply excited projectile states produced in the collision decay via x-ray cascades. The measurement of coincidences between two-projectile K-x rays associated with double electron capture at collision energies between 4.5 MeV/u and 11.5 MeV/u provides us with its excitation function for this resonant process which shows a strong enhancement at beam energies below 7.5 MeV/u in accordance with the expected resonance location. The cross sections found for this process are surprisingly large compared to the measured cross sections for resonant single-electron capture and excitation in Ge³¹⁺ → H₂ collisions. Considering also the non-correlated two-electron capture and excitation process we estimate for the resonant region a contribution of the non-resonant process to be about ⅓ of the measured cross section.