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

Dyke, John M., Lee, Edmond P.F., Mok, Daniel K.W. and Chau, Foo-tim (2005) A combined ab initio/Franck-Condon study of the Ã-X single-vibronic-level emission spectrum of CCl₂ and the photodetachment spectrum of CCl. ChemPhysChem, 6 (10), 2046-2059. (doi:10.1002/cphc.200500194).

Abstract

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^-.

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