Infrared spectra and Ab initio calculations for the F- - (CH4)n (n = 1-8) anion clusters

Abstract

Infrared spectra of mass-selected F- -(CH4) n (n = 1-8) clusters are recorded in the CH stretching region (2500-3100 cm-1). Spectra for the n = 1-3 clusters are interpreted with the aid of ab initio calculations at the MP2/6-311++G(2df 2p) level, which suggest that the CHU ligands bind to F- by equivalent, linear hydrogen bonds. Anharmonic frequencies for CH4 and F --CH4 are determined using the vibrational self-consistent field method with second-order perturbation theory correction. The n = 1 complex is predicted to have a C3v structure with a single CH group hydrogen bonded to F-. Its spectrum exhibits a parallel band associated with a stretching vibration of the hydrogen-bonded CH group ..