GUIDED ION-BEAM STUDIES OF REACTIONS OF ALKALINE-EARTH IONS WITH O2

The endothermic reactions of Mg+ and Sr+ with 02 are studied in a guid ed ion beam mass spectrometer. Analysis of the reaction thresholds are used to obtain 0 K bond dissociation energies of MgO+ (2.50 +/- 0. 10 eV) and SrO+ (3.47 +/- 0.06 eV), which are compared with other litera ture values. Analysis of these reaction cross sections and those previ ously published for the reaction of Ca+ with O2 [E.R. Fisher, J.L. Elk ind, D.E. Clemmer, R. Georgiadis, S.K. Loh, N. Aristov, L.S. Sunderlin , and P.B. Armentrout, J. Chem. Phys., 93 (1990) 2676] suggests that t here are both thermodynamic and impulsive reaction pathways. The latte r play an increasingly important role in the reaction dynamics as the mass of the alkaline earth ion increases.