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

Abstract

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 ²B₁ state, with the òB₂ and ã⁴Σ⁻_g state, calculated to be ca. 1.50 and 2.72 eV higher in energy respectively. The electron affinities of the ¹A₁ and ã³B₁ states of SnCl₂ have 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 (¹A₁) + e ← SnCl₂⁻ (²B₁) and SnCl₂ (ã³B₁) + e ← SnCl₂⁻ (²B₁) photodetachment bands have been simulated with computed Franck–Condon factors, which include an allowance for anharmonicity and Duschinsky rotation.