Dipole-allowed transitions between the X3Σ−, A′3∆, A′′3Σ+, A3Π, B3Σ−, and C3Π states of the sulfur monoxide radical

Abstract

The potential energy curves were calculated for the X3Σ−, A′3∆, A′′3Σ+, A3Π, B3Σ−, and C3Π states of the sulfur monoxide radical. The transition dipole moments between these states were computed. No dipole-allowed electronic emissions originate from the X3Σ−, A′3∆, and A′′3Σ+ states for the sake of symmetry and spin limitation. The rotationless radiative lifetimes of all vibrational levels are in the order of 10−5–10−6 s for the A3Π state, 10−7–10−8 s for the B3Σ− state, and 10−6 s for the C3Π state. The lifetimes of all vibrational levels indicate that the spontaneous emissions originating from the A3Π, B3Σ−, and C3Π states easily occur. Overall, the emissions from the A3Π–X3Σ−, B3Σ−–X3Σ−, C3Π–X3Σ−, A3Π –A′′3Σ+, C3Π–A3Π, and C3Π–A′′3Σ+ systems are strong, whereas the emissions from the B3Σ−–A3Π, C3Π–A′3∆ and C3Π–B3Σ− systems are so weak that they are very difficult to be measured in a spectroscopy experiment. The distribution of the spectral intensity is evaluated for spontaneous emissions of each system. The spontaneous emissions of the B3Σ−–X3Σ− system are so strong that they may potentially be measured in outer space, although the intense emissions of this system are in the visible and near-UV regions.