Geometries of the Halocarbene anions HCF − and CF 2−: ab initio calculation and Franck–Condon analysis

Abstract

A theoretical method to calculate multidimensional Franck–Condon factors including Duschinsky effects is described and used to simulate the photoelectron spectra of HCF − and CF 2 − radicals. Geometry optimization and harmonic vibrational frequency calculations have been performed on the X̃ 1A′ state of HCF and X̃ 2A″ state of HCF −, and X̃ 1A 1 state of CF 2 and X̃ 2B 1 state of CF 2 −. Franck–Condon analyses and spectral simulation were carried out on the first photoelectron band of HCF − and CF 2 −, respectively. The theoretical spectra obtained by employing B3LYP/6-311+G(2d,p) values are in excellent agreement with the observed ones. In addition, the equilibrium geometry parameters, R(CF)=0.1475±0.0005 nm, of the X̃ 2A″ state of HCF −, and r(FC)=0.1425±0.0005 nm and ∠(FCF)=100.5±0.5°, of the X̃ 2B i state of CF 2 −, are derived by employing an iterative Franck–Condon analysis procedure in the spectral simulation.