Diabatic capture in dissociative attachment

Abstract

Diabatic capture is shown to account for low energy dissociative attachment in alkyl bromides (RBr) and hydrogen halides. It is argued that low energy negative ion electronic resonances do not exist in these systems. The theory is tested by computations based on a one‐electron model, and agreement with experimental results is achieved for the hydrogen halides. Molecules (HF and RBr, in particular) which have a dipole moment greater than 1.625 D must have a positive vertical electron affinity. Information about the relation between the neutral molecule and negative ion potential curves is deduced using an isotope effect for HCl, HBr, and HI. The alkyl bromide and hydrogen halide negative molecular ions are all suggested to be stable when in isolation. Electron energy loss by vibrational excitation is discussed.