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

摘要

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 (X) over tilde B-2(1) state, with the (A) over tilde B-2(2) and (a) over tilde (4)Sigma(-)(g) state, calculated to be ca. 1.50 and 2.72 eV higher in energy respectively. The electron affinities of the (X) over tilde (1)A(1) and (a) over tilde B-3(1) 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 ((X) over tilde (1)A(1)) + e <- SnCl2- ((X) over tilde B-2(1)) and SnCl2 ((a) over tilde B-3(1)) + e <- SnCl2- ((X) over tilde B-2(1)) photodetachment bands have been simulated with computed Franck-Condon factors, which include an allowance for anharmonicity and Duschinsky rotation.