Effect of processes of vibrational kinetics of He2+ ions on afterglow of a discharge in helium

A disintegrating weakly ionized helium plasma (ne=(0.2-1.1)x1011 cm-3, p=(40-70) mm Hg) is experimentally studied. It is shown that the time dependences of intensities of atomic lines and molecular bands in the afterglow phase obtained in the experiments can be explained if vibrational kinetics of H2+ ions is taken into consideration. The analysis of the measurement results has shown that at ne or approx. 1018 cm-3 de-excitation of He2+ ions is principally due to inelastic collisions with helium atoms. On the basis of the experiment data the vibrational relaxation rate constant for helium molecular ions is estimated to be ∼ 10-16 cm3/s. These results are used in qualitative analysis of the He2+ ion distribution in vibrational states in the discharge phase