Emission spectrum of carbonyl sulfide in a helium afterglow

Photoemission from the following excited species was observed from OCS in a helium afterglow at wavelengths from 200 to 500 nm: OCS+(A2PI-X2PI), CO(A3PI-X1Σ+), CO+(A2PIsub(i)-X2Σ+, B2Σ+-X2Σ+), CS(A1PI-X1Σ+, a3PI-X1Σ+) and CS+(B2Σ+-A2PIsub(i)). The dependence of emission intensities on the electrostatic potential applied to an ion-collector grid indicated that OCS+(A-X) emission results from He(23S) Penning ionization, while CO+(A-X,B-X) emission is the result of dissociative charge-transfer ionization of OCS with He+ ions. The emission rate constants were estimated to be 5.1 +- 0.5 x 10-13 cm3 molecule-1 s-1 for OCS+(A) and about 9 x 10-12 cm3 molecule-1s-1 for CO+(A). Energy resonance was found to be an important factor for the thermal He+/OCS reaction. (orig.)