Transition properties between the a1Δ, b1Σ+, c1Σ−, d1Π, and e1Π states of sulfur monoxide radical

Abstract

Almost all spontaneous vibronic emissions arising from the singlet states of sulfur monoxide radical have not been measured experimentally up to date. For this reason, this work studies the transition properties between the a1Δ, b1Σ+, c1Σ−, d1Π, and e1Π states. The potential energy curves of these singlet states and the transition dipole moments between them are calculated using the complete active space self-consistent field method, which is followed by the internally contracted multireference configuration interaction approach. The radiative lifetimes are in the order of 100 ns for all vibrational levels of the d1Π and e1Π states, suggesting that the vibronic emissions originating from them occur easily. Overall, the emissions of the d1Π – a1Δ, d1Π – b1Σ+, e1Π – a1Δ, and e1Π – c1Σ− systems are strong, indicating that they are not difficult to measure via spectroscopy. The e1Π – d1Π transitions are so weak that it is difficult to detect them by spectroscopy. For the d1Π – a1Δ, e1Π – a1Δ, and e1Π – b1Σ+ transitions, the spectral range of strong emissions are in the UV region. For the d1Π – b1Σ+ system, most of the strong emissions are of UV light; only a few are of visible light. For the d1Π – c1Σ− and e1Π – c1Σ− transitions, most of the strong emissions are of visible light. The distribution of radiative lifetime with the variation of rotational quantum number is studied for a certain vibrational level of the d1Π and e1Π states. The transition properties reported in this study can be used to measure the vibronic emissions originating from these states, both in laboratory and in outer space.