Radiative and nonradiative collisional deexcitation of metastable hydrogen-like ions

A method is presented to measure separate cross sections for collisional de excitation of metastable ions via radiative and non-radiative processes. Th e principle of the experiment is to first determine the total collisional d eexcitation cross section in an attenuation-like measurement. After this th e non-radiative part is determined separately in a measurement where the io nized target atom (unique to the non-radiative process) is detected. Here w e discuss recently published results on deexcitation of metastable He+(2s) ions colliding with Ar at 1.65 keV/amu [H. T. Schmidt et al., Phys. Rev A 5 7, R4082 (1998) and Phys. Rev. A 58 (1998)] as well as preliminary results for a Xe target. In both cases we find that the dominating contribution fro m radiative deexcitation agrees with the result of a semi-classical calcula tion of the 2s-2p mixing driven by the induced dipole held of the target at om modified by taking competing processes, for which we measured the cross sections, into account. Finally the extension to H-like projectile ions in higher charge states is discussed.