Transition properties of a2Σ–, b2Δ, c2Π, d2Π, and e2Σ+ electronic states of aluminum silicon radical

Abstract

Detecting aluminum silicon can yield useful information concerning the depletion of silicon and aluminum and their recycling in astrophysical sources. In addition, such detection can be helpful for understanding gas–phase aluminum and silicon chemistry in the interstellar/circumstellar atmosphere. However, only a few transition properties of this radical have been reported. Therefore, the potential energy curves of several lowest–lying doublet states and the transition dipole moments between them were calculated using the icMRCI approach. Core–valence correlation correction, scalar relativistic correction, and spin–orbit coupling effect were included to improve the accuracy of transition properties. The radiative lifetimes of the first 16 levels were approximately 4.8 – 679.5 ms for the c2Π1/2 state, 2.2 – 431 ms for the c2Π3/2 state, 29.3 – 40.4 µs for the d2Π1/2 state, 21.2 – 30.1 µs for the d2Π3/2 state, and 88.7 – 175.6 µs for the e2Σ+1/2 state. The spontaneous emissions from the c2Π1/2 and c2Π3/2 states to the a2Σ–1/2, b2Δ3/2, and b2Δ5/2 states and those from the e2Σ+1/2 state to the d2Π1/2 and d2Π3/2 states were located in the radio–frequency region. The d2Π1/2 – a2Σ–1/2 and d2Π3/2 – a2Σ–1/2 transitions were the strongest, followed by d2Π1/2 – b2Δ3/2, d2Π3/2 – b2Δ3/2, d2Π3/2 – b2Δ5/2, d2Π1/2 – c2Π1/2, d2Π3/2 – c2Π3/2, e2Σ+1/2 – c2Π1/2, and e2Σ+1/2 – c2Π3/2 transitions. The spontaneous emissions from these systems were located in the infrared region. The variation in the radiative lifetime of a level υ versus the rotational quantum number J was investigated for the d2Π1/2, d2Π3/2, and e2Σ+1/2 states.