CS+ (B 2Σ+--X 2Σ+) emission produced from Penning ionization of the CS (X1 Σ+) radical

Emission spectrum resulting from the energy transfer reaction of He (2 3S) with transient CS radical produced through a microwave discharge of Ar/CS2 mixture was observed in a flowing afterglow apparatus. A new CS+ (B 2Σ+--X 2Σ+) band system due to He (2 3S)/CS Penning ionization was identified in the 220--340 nm region. The dominant bands were the (ν',0) and (0, ν'') progressions, which was consistent with the prediction from calculated Morse potential Franck--Condon factors. Although the observed bandhead wavelengths of the major CS+ (B--X) emission were in good agreement with those predicted from the reported spectroscopic data, the (4,0) band was located at an abnormal position. It was interpreted as a consequence of vibrational perturbation in the B 2Σ+ state. The relative intensities of CS+(B--X), CS+(B--A), CI, and SI emission were estimated to represent that the dominant pathway of the He (2 3S)/CS reaction is Penning ionization