Simulation of ù B₁→ X˜¹A₁CF₂single vibronic level emissions : including anharmonic and Duschinsky effects

Abstract

CASSCF/MRCI/aug-cc-pVQZ(no g) and RCCSD(T)/aug-cc-pVQZ potential energy functions were reported for the ùB₁and X˜¹A₁states of CF₂, respectively. Vibrational wave functions of the symmetric stretching and bending modes of the two states of CF₂were obtained in variational calculations, employing Watson’s Hamiltonian for a nonlinear molecule and anharmonic vibrational wave functions expressed as linear combinations of harmonic basis functions. Franck–Condon factors (FCFs) were computed for ùB₁→ X˜¹A₁CF₂single vibronic level (SVL) emissions and the SVL emission spectra were simulated with the computed FCFs. When compared with the observed spectra, the simulated spectra obtained in the present investigation, which include allowance for anharmonicity and the Duschinsky effect, were found to be significantly superior to those reported previously, based on the harmonic oscillator model. Using the iterative Franck–Condon analysis procedure, with the geometry of the X˜¹A₁state fixed at the recently determined experimental equilibrium geometry, the geometry of the à ¹B₁state of CF₂, which gave the best match between simulated and observed spectra, was found to be rₑ(CF)=1.317Å and θₑ(FCF)= 121.25 °.