Multireference configuration interaction study of ground and low-lying excited states of the AlC radical

Abstract

ABSTRACTThis work explored the spectroscopic parameters and vibrational properties of the 21 Λ–S and 42 Ω states of the AlC radical. The PECs were calculated with the CASSCF method, which was followed by the icMRCI+Q approach. The A4Π, a2Π, 52Π, 22Δ, and 12Φ states as well as the first well of B4Σ− state were inverted with the spin–orbit coupling (SOC) effect included; the 14Δ, 14Σ+, and 22Σ− states as well as the second wells of the B4Σ−, 22Σ+, 32Σ+, 42Π and 52Π states were weakly bound, which well depths were less than 650 cm−1; the B4Σ−, 22Σ+, 32Σ+, 42Π, 52Π, and 22Δ states had double wells and the second wells of these states except for B4Σ− had only several vibrational states; the avoided crossings existed between the 22Σ+ and 32Σ+ states, the 32Σ+ and 42Σ+ states, the B4Σ− and 34Σ− states, the 22Δ and 32Δ states, the 42Π and 52Π states, the 52Π and 62Π states, as well as the 24Π and 34Π states. The extrapolation scheme, core–valence correlation and scalar relativistic corrections were included. The spectroscopic parameters and vibrational properties were determined. The TDM curves between two different Λ–S states were calculated and Franck–Condon factors of some transitions were evaluated. The SOC effect on the spectroscopic and vibrational properties was evaluated.