Transition properties of five lowest–lying singlet and three lowest–lying triplet states of silicon monosulphide molecule

Abstract The transition properties of the X1Σ+, C1Σ–, D1Δ, A1Π, E1Σ+, a3Σ+, d3Δ, and b3Π states of silicon monosulphide were investigated using the complete active space self-consistent field method, which was followed by the internally contracted multireference configuration interaction approach. The transition dipole moments were calculated for the dipole–allowed transitions between these singlet states and for all transitions between the X1Σ+, a3Σ+, d3Δ, and b3Π states. The radiative lifetimes of the first 16 vibrational levels were 107.6 – 120.5 ns for the A1Π state and 12.8 – 14.1 ns for the E1Σ+ state. Among these dipole–allowed transitions, the emissions from the A1Π – X1Σ+ and E1Σ+ – X1Σ+ systems were strong, whereas those from the b3Π – d3Δ system were weak. The radiative lifetimes of the first 16 levels were 4.3 – 9.8, 3.8 – 35.4, 2.2 – 7.9, and 11.9 – 14.5 ms for the a3Σ+1, a3Σ+0–, d3Δ1, and d3Δ2 states, respectively. These were 117 – 380, 73 – 581, and 137 – 586 μs for the b3Π0+, b3Π1, and b3Π2 states, respectively. Among these forbidden transitions, the b3Π0+ – X1Σ+0+ and b3Π1 – X1Σ+0+ transitions were the strongest. The Franck–Condon factors, Einstein A coefficients, and band origins of all these spontaneous emissions were calculated. The transition properties were compared with the available experimental and theoretical results.