Ab initio study of the lowest 3Σ-, 3Π and 1Σ+ states of the SiN+ cation

Abstract

The equilibrium bond lengths, harmonic frequencies, first-order anharmonicity constants, rotational constants, centrifugal distortion constants, and rotation-vibrational constants, as well as the dipole moments, excitation and dissociation energies for the lowest (3)Sigma(-), (II)-I-3 and (1)Sigma(+) states of SiN+ have been calculated using CASSCF, CMRCI, CCSD(T) and density functional (B3LYP and B3PW91) theories combined with Dunning's correlation-consistent basis sets. Core-correlation effects have also been included in order to obtain a satisfactory accuracy for the spectroscopic constants. Our calculations strongly support (3)Sigma(-) as the ground state; the (II)-I-3 state lies only 460 cm(-1) above the (3)Sigma(-) state, while the (1)Sigma(+) state lies 6865 cm(-1) above the ground state. Our DFT calculations on the triplet surface of SiN+ converge to the (II)-I-3 state which is clearly not the ground state. (C) 1999 Elsevier Science B.V. All rights reserved.