Determination of the molecular constants of interacting bright and dark states: Analysis of the high-resolution infrared spectrum of the S–O stretching fundamental of thionylimide, HNSO

Abstract

The S–O stretching fundamental, ν2, of thionylimide has been recorded at high resolution and rotationally analyzed for the first time. This strong A-type band with origin at 1257.5808 cm−1 is extensively perturbed by the 5161 state at 1206.58 cm−1 through a- and b-axis Coriolis interactions. Even though no ν5+ν6 band transitions could be found, a complete analysis of the perturbed rotational structure has been achieved. Accurate molecular constants for the ‘‘bright’’ 21 state and the ‘‘dark’’ 5161 state have been obtained, using a Hamiltonian that includes both types of Coriolis interactions. Further small perturbations at high Ka and J have been identified as higher-order interactions with the ν3 band at much lower energy.