Configuration interaction calculations on the spectroscopic and transition properties of magnesium chloride**Project supported by the National Natural Science Foundation of China (Grand Nos. 11564019, 11147158, 11264020, and 11574114) and Jiangxi Provincial Education Department Project, China (Grand No. GJJ170654).

Abstract

The potential energy curves (PECs) of 14 Λ–S states for magnesium chloride (MgCl) have been calculated by using multi-reference configuration interaction method with Davidson correction (MRCI + Q). The core-valence correlation (CV), scalar relativistic effect, and spin–orbit coupling (SOC) effect are considered in the electronic structure computations. The spectroscopic constants of X2Σ+ and A2Π states have been obtained, which are in good agreement with the existing theoretical and experimental results. Furthermore, other higher electronic states are also characterized. The permanent dipole moments (PDMs) of Λ–S states and the spinorbit (SO) matrix elements between Λ–S states are also computed. The results indicate that the abrupt changes of PDMs and the SO matrix elements are attributed to the avoided crossing between the states with the same symmetry. The SOC effect is taken into account with Breit–Pauli operator, which makes the 14 Λ–S states split into 30 Ω states, and leads to a double-well potential of the Ω = (3)1/2 state. The energy splitting for the A2Π is calculated to be 53.61 cm−1 and in good agreement with the experimental result 54.47 cm−1. The transition dipole moments (TDMs), Franck–Condon factors (FCFs), and the corresponding radiative lifetimes of the selected transitions from excited Ω states to the ground state X2Σ + 1/2 have been reported. The computed radiative lifetimes τν′ of low-lying excites Ω states are all on the order of 10 ns. Finally, the feasibility of laser cooling of MgCl molecule has been analyzed.