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(+)((2)P(u)) + O((3)P(g)) and Si(+)((2)P(u)) + O((1)D(g))), have been calculated at the internally contracted multireference configuration interaction (CMRCI) level with Dunning's correlation-consistent polarized valence quadruple zeta (cc-pVQZ) basis set. The equilibrium bond lengths (r(e)), harmonic frequencies (omega(e)), first- and second-order anharmonicity constants (omega(e)x(e), omega(e)y(e)), rotational constants (B(e)), vibrational separations (DeltaG(1/2)), dipole moments (µ(e)), excitation (T(e)), and dissociation energies (D(e)) for eight bound doublet states (X(2)Sigma(+), A(2)Pi, B(2)Sigma(+), (2)(2)Delta, (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(-)) have 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 experimental data. The dipole-allowed transition moments between the studied doublet states of SiO(+) have also been calculated at the same theoretical level. Based on both the computed potential energy curves and the electronic transition moments, radiative lifetimes for the bound electronic excited states at the v' = 0, 1, and 2 vibrational levels have been calculated. The lifetimes of the B(2)Sigma(+) ( Kv' = 0, 1, and 2) states are in excellent agreement with recent experimental data. Copyright 1999 Academic Press.