Spectroscopic Parameters of X3Σ−, a1Δ, and A′3Δ Electronic States of SO Radical

Abstract

The potential energy curves (PECs) of three low-lying electronic states (X3Σ, a1Δ, and A′3Δ) of SO radical have been studied by ab initio quantum chemical method. The calculations were carried out with the full valence complete active space self-consistent field method followed by the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with correlation-consistent basis sets. Effects of the core-valence correlation and relativistic corrections on the PECs are taken into account. The core-valence correlation correction is carried out with the cc-pCVDZ basis set. The way to consider the relativistic correction is to use the second-order Douglas-Kroll Hamiltonian approximation, and the correction is performed at the level of cc-pV5Z basis set. To obtain more reliable results, the PECs determined by the MRCI calculations are also corrected for size-extensivity errors by means of the Davidson modification (MRCI+Q). These PECs are extrapolated to the complete basis set limit by the two-point energy extrapolation scheme. With these PECs, the spectroscopic parameters are determined.