A combined ab initio/Franck-Condon study of the Ã-X single-vibronic-level emission spectrum of CCl₂ and the photodetachment spectrum of CCl

State-of-the-art ab initio calculations have been carried out on the X1A1, a3B1 and A1B1 states of CCl2 and the (XB1)-B-2 state of CCl2-. Franck-Condon factors including anharmonicity have been calculated, between the CCl2 states, and between the CCl2- X2B1 state and the CCl2 states. They are used to simulate the A-X single-vibronic-level (SVL) emission spectra of CCl2 determined by MA. Lui et a]. [PCCP 2003, 5, 352] and the 364 nm laser photo detachment spectrum of CCl2- obtained by R. L. Schwartz et al. [J. Phys. Chem. A 7999, 103, 8213]. Comparison between simulated and observed spectra confirms the vibrational assignments of the X2B1 SVL emission spectra and the T0 position of the A(1)B1 state of CCl2. For the photodetachment spectrum of CCl2-, spectral simulation shows that the higher binding energy 6 3 B, (CCl2) CCl2-X2B1 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 CC12. These calculations identify the anionic state to be the lowest (4)Sigma(g)(-) ((4)Sigma(-)) state, which photodetaches vertically to the (3)Sigma(g)(-) ((3)Sigma(-); adiabatically a3B1 and/or (3)Pi(u) ((3)Pi) states of CCl2 to give the second band observed in the 364 nm photodetachment spectrum of CCl2-