Calculation of Franck-Condon factors and simulation of photoelectron spectra of the HCCl− anion: Including Duschinsky effects

Halomethylenes (such as HCCl) are particularly critical intermediates in many gas-phase reaction environments. The structures, spectra, and reactivity of environment-related molecules have been of many studies interest. In the present work, geometry optimization and frequency calculations have been carried out on the X˜2A″ state of HCCl− and the X˜1A′ and a˜3A″ states of HCCl at CCSD(T) theory. The single point energy, electron affinity and term energy of HCCl have been computed up to the CCSD(T)/aug-cc-pV5Z level and extrapolated to the complete basis set limit. The Duschinsky matrix and displacement vector have been considered at the CCSD(T) level of theory and the result shows that the normal mode mixing effects play a main role for HCCl(a˜3A″)-HCCl−(X˜2A″) transition, and which can be neglected for the HCCl(X˜1A′)-HCCl−(X˜2A″) process. Franck-Condon analysis and spectral simulations have been performed on the singlet and triplet photo-detachment processes, respectively. We have merged the singlet and triplet transitions together for the first time and the results show that the simulated spectra are very consistent with the previous experimental one.