Determination of the rate constants for population of the individual Cd+* levels in thermal Penning and charge transfer reactions of He*(23S1) and He+with cadmium

Abstract

Thermal, Penning and charge transfer reactions of He*(23S1) metastable atoms and He+ ions with cadmium were studied in a flowing afterglow apparatus. The absolute values of the rate constants for excitation of the individual Cd+* levels have been measured. In Penning ionisation, only 22 and 13% of the Cd+ ions are produced in the upper levels of the 441.6 and 325.0 nm laser lines respectively, and 40% of them are directly formed in the Cd+ ground state. In charge transfer reactions, the part of the Cd+ ions excited in the five high-lying 9p 2P, 8d 2D, 6g 2G, 6f 2F and 9s 2S states is almost half of the product Cd+ ion, the remaining half being distributed between other excited levels of Cd+ down to a few eV below the energy of the He+ ion. The authors also measured the total Penning ionisation and charge transfer rate constants: k=(8.0+or-1.5)*10-10 cm3 s-1 and k=(5.5*1.0)*10-10 cm3 s-1 respectively.