Radiative lifetimes and transition properties of boron monoxide cation

Abstract

The transition dipole moments of dipole–allowed transitions between the following states were calculated in this study: X1Σ+, A1Π, B1Σ+, C1Δ, D1Σ–, and E1Π; a3Π, b3Σ+, c3Σ–, d3Π, and e3Δ, and those of the spin–forbidden transitions from the a3Π state to the X1Σ+ state of boron monoxide cation. The CASSCF method was used, followed by the valence icMRCI approach. The radiative lifetimes of the vibrational states were of the order of 1 – 10 μs for the A1Π state; 10 ns for the D1Σ–, e3Δ, and the first well of the B1Σ+ states; 1 – 1000 ns for the second well of the B1Σ+ state; 100 ns for the d3Π state; 0.1 – 1 μs for the b3Σ+ and E1Π states; 10 – 100 μs for the C1Δ state; and 10 – 10,000 μs for the c3Σ– state. The transition from the first well of the B1Σ+ state to the X1Σ+ state and that from the double well of the B1Σ+ state to the A1Π state were the strongest, followed by the D1Σ– – A1Π, E1Π – A1Π, d3Π – a3Π, and e3Δ – a3Π transitions. The transition from the second well of the B1Σ+ state to the X1Σ+ state was the weakest, followed by the C1Δ – A1Π, E1Π – B1Σ+, E1Π – C1Δ, E1Π – D1Σ–, c3Σ– – a3Π, and e3Δ – d3Π transitions. The variation in the radiative–lifetime distribution with the rotational angular quantum number J was evaluated. The radiative lifetimes of the vibrational states were of the order of 1 – 10 ms for the a3Π1 state and 10 ms for the a3Π0+ state. The a3Π1 – X1Σ+0+ and a3Π0+ – X1Σ+0+ transitions were weak. The transition properties reported herein may provide useful guidelines for related experimental and theoretical investigations in the near future.