XeF⁺, IF⁺, and other unusual ions generated by reactions of hyperthermal ion beams at self-assembled monolayer surfaces

Abstract

Collisions of atomic and molecular ions (I(+), Xe(+); CH3I(+), I 2 (+) ) with self-assembled fluoroalkyl-monolayer surfaces result in reactions involving the net transfer of fluorine atoms or fluorocarbon radicals from the surface to the projectile ions. The scattered products, which include unusual ionic species such as IF(+), IF 2 (+) CFI(+); CF2I(+), I2F(+), and XeF(+), are generated in endothermic ion-surface reactions. These reactions are not observed when the collision partner is a gas-phase (rather than a surface-bound) perfluoroalkane. Evidence is presented which suggests that in some cases molecular projectiles undergo surface-induced dissociation to yield atomic species which subsequently react with the surface. Fluorine abstraction is favored for projectiles containing highly polarizable elements.