Optical Spectroscopic Studies on Penning Ionization and Charge-Transfer Reactions at Thermal Energy by Using Flowing Afterglow

Abstract

The flowing afterglow apparatus has been coupled with a low pressure chamber by a small orifice for optical spectroscopic studies on Penning ioniza­ tion and charge-transfer reactions under single collision conditions. Nascent rovibrational distributions are determined from a spectral simulation. As selected examples, detailed results are reported about non-Franck-Condon type He(2 3 S)/02 Penning ionization and near-resonant He+ /H20, D20 charge-transfer reactions. A brief summary is also given of our optical spectroscopic studies by using the conventional flowing afterglow apparatus. The flowing afterglow (FA) method was developed in 1963 by Ferguson and his co-workers of NOAA Laboratories in Boulder, Colorado, for the study of ion-molecule reactions in the earth's atmosphere.o The main emphasis of their studies was placed upon measurements of formation rate constants and branching ratios of ionic products by using a mass spectrometer. More than a few thousands kinetic data at (near) thermal energy were compiled in the reported tables. 2 ) In our laboratory, the FA coupled with a DV and visible emission detection system has been used for studying the following ionization processes in collisions of metastable atoms (M*) and ions (M+) with a molecule (AB): M*+AB~ABH+M+e-, (Penning ionization) (1) ~ A H + B + M + e-, (Dissociative Penning ionization) (2)