RADIATIVE AND NONRADIATIVE COLLISIONAL DEEXCITATION OF METASTABLE HYDROGEN-LIKE IONS

A method is presented to measure separate cross sections for collisional deexcitation of metastable ions via radiative and non-radiative processes. The principle of the experiment is to first determine the total collisional deexcitation cross section in an attenuation-like measurement. After this the non-radiative part is determined separately in a measurement where the ionized target atom (unique to the non-radiative process) is detected. Here we discuss recently published results on deexcitation of metastable He+(2s) ions colliding with Ar at 1.65 keV/amu (H T Schmidt et al 1998 Phys. Rev. A 57 R4082 and 1998 Phys. Rev. A 58) as well as preliminary results for a Xe target. In both cases we find that the dominating contribution from radiative deexcitation agrees with the result of a semi-classical calculation of the 2s-2p mixing driven by the induced dipole field of the target atom 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.