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

Thermal, Penning and charge transfer reactions of He*(2 3 S 1 ) 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 2 P, 8d 2 D, 6g 2 G, 6f 2 F and 9s 2 S 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 cm 3 s -1 and k=(5.5*1.0)*10 -10 cm 3 s -1 respectively.