TRANSLATIONAL ENERGY-SPECTRA FOR SINGLE-ELECTRON CAPTURE BY O2+ IN HE, NE, AND AR

High-resolution single-electron capture spectra have been obtained for O2+ ions colliding with He, Ne, and Ar at 4-keV energy. For the He an d Ne targets the dominant capture channels involve transitions from th e ground 3p state of O2+ to the first and second excited states (2D0 a nd 2P0 of O+. Eight well-resolved peaks are observed in each spectrum, corresponding to exactly the same capture channels with the target pr oduct ions (He+ and Ne+) undisturbed in their ground states. One relat ively intense peak observed in the Ne spectrum is attributed to captur e from the quintet state of O2+ (2s2p3 S-5(0) to the 4P state of O+ (2 s2p4 4P). The O2+ in the Ar spectrum exhibits an entirely different ch aracter. Eight peaks are discernible, of which five are associated wit h capture channels which leave the target product Ar+ ion in an excite d state. The dominant channel is due to the ground-to-ground transitio n O2+(3P)-->O+(S-4(0)) with the target Ar+ ion formed in its first exc ited state (3s3p6 2S).