The splitting of low-lying states for hydroxyl molecule under spin–orbit coupling

Abstract

The splitting of potential energy curves for the states X2Π3/2, 2Π1/2 and A2Σ+ of hydroxyl OH under spin–orbit coupling (SOC) has been calculated by using the SO multi-configuration quasi-degenerate perturbation theory (SO-MCQDPT). Their Murrell–Sorbie (M–S) potential functions have been derived, then, the spectroscopic constants for X2Π3/2,2Π1/2 and A2Σ+ have been derived from the M–S function. The calculated dissociation energies for the three states are D0[OH(X2Π3/2)]=34966.632cm−1, D0[OH(2Π1/2)]=34922.802cm−1 and D0[OH(A2Σ+)]=17469.794cm−1, respectively. The vertical excitation energy ν[2Π1/2(ν = 0)→X2Π3/2(ν = 0)] = 139.6cm−1. All the spectroscopic data for the X2Π3/2 and 2Π1/2 are given for the first time except the dissociation energy of X2Π3/2.