Collisional excitation and destruction of excited Zn II levels in a helium afterglow

Abstract

The processes which excite and de-excite levels of the zinc ion in a helium afterglow containing zinc vapour are studied using a flowing afterglow technique. It is shown that thermal energy charge transfer reactions between atomic helium ions and ground state zinc atoms result primarily in the excitation of the 6p2P and 5d2D levels of Zn II. The 6s2S levels receive their excitation via radiative cascade from the 6p2P levels. The 4f2F levels are excited by a two step process: charge transfer excitation into 4f2F. The collisional destruction rate of the 6p2P levels of Zn II is also measured. The observed collision processes are significant not only for the understanding of the He-Zn laser but also because of their implications for power output capabilities of charge transfer excited laser systems in general.