A combined ab initio/Franck-Condon study of the Ã-X̃ single-vibronic-level emission spectrum of CCl₂and the photodetachment spectrum of CCl₂

State-of-the-art ab initio calculations have been carried out on the X̃1A1, ã3B1and Ã1B1states of CCl2and the X̃2B1state of CCl21. Franck-Condon factors including anharmonicity have been calculated, between the CCl2states, and between the CCl2-X̃2B1state and the CCl2states. They are used to simulate the Ã-X̃ single-vibronic-level (SVL) emission spectra of CCl2determined by M.-L. Lui et al. [PCCP 2003, 5, 352] and the 364 nm laser photodetachment spectrum of CCl2-obtained by R. L. Schwartz et al. [J. Phys. Chem. A 1999, 103, 8213]. Comparison between simulated and observed spectra confirms the vibrational assignments of the X̃2B1SVL emission spectra and the T0position of the Ã1B1state of CCl2. For the photodetachment spectrum of CCl2-, spectral simulation shows that the higher binding energy ã3B1(CCl2)→X̃2B1(CCl2-) band is well separated from the X̃1A1(CCl2)→X̃2B1(CCl2-) bond. It is concluded that the observed second band, which overlaps heavily with the X̃1A1(CCl2)→X̃2B1(CCl2-) band in the photodetachment spectrum of CCl2-cannot be assigned to the CCl2(ã3B1)+e→CCl2-(X̃2B1) detachment process. Further ab initio calculations carried out in the present investigation support the suggestion that the second band in the 364 nm photodetachment spectrum of CCl2-is due to detachment from an excited state of CCl2-, a linear quartet state, to a triplet state of CCl2. These calculations identify the anionic state to be the lowest4Σg(4Σ-) state, which photodetaches vertically to the3Σg(3Σ-; adiabatically ã3B1) and/or3Πu(3Π) states of CCl2to give the second band observed in the 364 nm photodetachment spectrum of CCl2-. KGaA.