Excitation of Zn⁺* levels in Penning and charge transfer reactions of He*(2³S₁) and He⁺with zinc

Thermal, Penning and charge transfer reactions of He*(2 3 S 1 ) metastable atoms and He + ions with zinc were studied in a flowing afterglow apparatus. The absolute values of the rate constants for excitation of the individual Zn + * levels have been measured. In Penning ionisation only 3.2 and 2.0% of the Zn + ions are produced in the states which correspond to upper levels of the 747.9 and 589.4 nm laser lines respectively, while 90% of the ions are directly formed in the ground state. In charge transfer reactions, the fraction of the Zn + ions excited in the four high lying 6p 2 P, 5d 2 D, 4f 2 F and 6s 2 S states is about half of the product Zn + ions, 45% being produced in 5d 2 D levels. The remaining half are equally distributed between levels of the 3d 9 4s( 3 D)4p configuration and other levels down to a few eV below the energy of the He + ion. The authors have also measured the total Penning ionisation and charge transfer rate constants: k(PI)=(7.1+or-1.4)*10 -10 cm 3 s -1 and k(CT)=(7.4+or-1.4)*10 -10 cm 3 s -1 respectively.