EFFECTS OF COMPOSITION, STRUCTURE, AND H ATOM ADDITION ON THE CHEMISTRY OF BORON-OXIDE CLUSTER IONS WITH HF

We have studied reactions of thermalized, mass-selected boron oxide (H BnOm+, n = 1-3, m = 1-4) and hydrogenated boron oxide (HBnOm+, n = 1, 2, m = 1-3) ions with HF. Cross sections are reported for each product channel for collision energies ranging from 0.1 to 10 eV (center of m ass). On the basis of the observed collision energy dependence, produc t branching, and effects of hydrogenation, we propose a reaction mecha nism where facile reaction occurs only at certain sites on the oxide, most likely at terminal -B=O groups. H atom addition greatly decreases reactivity, apparently by blocking the reactive sites. Our data also point out several significant uncertainties in the literature thermoch emistry for B/O/F/H species, and we are able to give some limits on De lta H-f for several molecules.