An ab initio study on the ground and low-lying doublet electronic states of SbO2

Abstract

Geometry optimization and harmonic vibrational frequency calculations have been carried out on the low-lying doublet electronic states of antimony dioxide ͑SbO 2 ͒ employing a variety of ab initio methods, including the complete active space self-consistent field/multireference configuration interaction and the RCCSD͑T͒ methods. Both large and small core relativistic effective core potentials were used for Sb in these calculations, together with valence basis sets of up to aug-cc-pV5Z quality. Contributions from outer core correlation and off-diagonal spin-orbit interaction to relative electronic energies have been calculated. The ground electronic state of SbO 2 is determined to be the X 2 A 1 state, as is the case for dioxides of other lighter group 15 p-block ͑or group VA͒ elements. However, the à 2 B 2 and B 2 A 2 states are estimated to be only 4.1 and 10.7 kcal/ mole above the X 2 A 1 state, respectively, at the complete basis set limit. Reliable vertical excitation energies from the X 2 A 1 state to low-lying excited states of SbO 2 have been computed with a view to assist future spectral assignments of the absorption and/or laser-induced fluorescence spectra of SbO 2 , when they become available.

Ab initio calculations on the X̃ B21 and à A21 states of AsH2, and Franck–Condon simulation, including anharmonicity, of the Ã(,,)-X̃ single vibronic level emission spectrum of AsH2

“…From our previous investigation on low-lying electronic states of SbO 2 , it was found that, while effects of outer core correlation of the Sb 4d 10 electrons on optimized geometrical parameters and computed relative electronic energies are considerable, core correlation effects arising from the Sb 4s 2 4p 6 electrons are insignificantly small. 22 Since As is above Sb in the Periodic Table, core correlation effects of the As 3s 2 3p 6 electrons on computed molecular properties are expected to be weaker than those of the Sb 4s 2 4p 6 electrons, because the energy separations between the outer core 3s3p shells and the valence 4s4p shells of As are larger than the corresponding separations between the outer core 4s4p shells and the valence 5s5p shells of Sb. In view of the above considerations, it is concluded that including only outer core correlation of As 3d 10 electrons in the present study on AsH 2 should be adequate.…”