DYNAMICS OF PENNING IONIZATION REACTIONS INVOLVING HE(2(3)S) METASTABLE ATOMS

Spin-labeling techniques, specifically the use of electron-spin-polari zed He(2S-3) metastable atoms coupled with energy-resolved spin analys is of the product electrons, are used to investigate the dynamics of P enning ionization in collisions between He(2S-3) atoms and H2O, SO2, N O, and NO2. The data complement earlier studies of the reaction dynami cs based on analysis of the energy distribution of the product electro ns and confirm that ionization can occur via a number of different rea ction channels. For example, the present results show that in collisio ns with targets having a positive electron affinity, ionization via th e ionic channel is important and that effects due to spin-orbit coupli ng must be considered. The data also provide evidence that exchange ma y be important in collisions with open-shell targets.