Ab initio study of the electronic spectrum of the SiO+ cation

The potential energy curves of the SiO+ cation for the low-lying electronic states, correlating to the first two lowest dissociation channels (Si+(P-2 (u)) + O(P-3(g)) and Si+(P-2(u)) + O(D-1(g))), have been calculated at the internally contracted multireference configuration interaction (CMRCI) leve l with Dunning's correlation-consistent polarized valence quadruple zeta (c c-pVQZ) basis set. The equilibrium bond lengths (r(e),), harmonic frequenci es to the first- and second-ol der anharmonicity constants (w(e)x(e), w(e)y (e)), rotational constants (B-e), vibrational separations (Delta G(1/2)), d ipole moments (mu(e)), excitation (T-e), and dissociation energies (D-e) fo r eight bound doublet states (X(2)Sigma(+), A(2)Pi, B(2)Sigma(+), (2)(2)Del ta, (3)(2)Sigma(+), (4)(2)Pi, (3)(2)Sigma(-), and (1)(2)phi) and four bound quartet states (a(4)Sigma(+), (1)(4)Pi, (1)(4)Delta, and(1)(4)Sigma(-)) ha ve been calculated. The spectroscopic constants for the X(2)Sigma(+) A(2)Pi , and B(2)Sigma(+) states are in good agreement with the available experime ntal data. The dipole-allowed transition moments between the studied double t states of SiO+ have also been calculated at the same theoretical level. B ased on both the computed potential energy curves and the electronic transi tion moments, radiative lifetimes for the bound electronic excited states a t the v' = 0, 1, and 2 vibrational levels have been calculated. The lifetim es of the B(2)Sigma(+) (v' = 0. 1, and 2) states ale in excellent agreement with recent experimental data. (C) 1999 Academic Press.