Ab initio calculations on low-lying electronic states of SnCl₂^-and Franck-Condon simulation of its photodetachment spectrum

Geometry optimization and harmonic vibrational frequency calculations have been carried out on low-lying doublet and quartet electronic states of stannous (tin(ii)) dichloride anion (SnCl2-) employing the CASSCF and RCCSD(T) methods. The small-core fully-relativistic effective core potential, ECP28MDF, was used for Sn in these calculations, together with valence basis sets of up to augmented correlation-consistent polarized-valence quintuple-zeta (aug-cc-pV5Z) quality. The ground electronic state of SnCl2-is determined to be the X̃2B1state, with the Ã2B2and ã4Σ-g state, calculated to be ca. 1.50 and 2.72 eV higher in energy respectively. The electron affinities of the X̃1A1and ã3B1states of SnCl2have been computed to be 1.568 ± 0.007 and 4.458 ± 0.002 eV respectively, including contributions of core correlation and extrapolation to the complete basis set limit. The SnCl2(X̃1A1) + e ← SnCl2-(X̃2B1) and SnCl2(ã3B1) + e ← SnCl2-(X̃2B1) photodetachment bands have been simulated with computed Franck-Condon factors, which include an allowance for anharmonicity and Duschinsky rotation.