Spin-forbidden electronic transition properties of MgO

The spin-forbidden transitions of MgO are very important to the photodissociation dynamics and chemical reaction dynamics, which are frequently occurred in the interstellar space. In this work, the internally contracted multireference configuration interaction (icMRCI) method with the Davidson correction is used to compute the adiabatic potential energy curves (PECs) of eight Lambda-S electronic states of MgO. Through considering the spin-orbit coupling (SOC) effect, the PECs of six splitting electronic states and the spin-forbidden transition dipole moments (TDMs) between the six lowest lying Omega states are also calculated. Using the calculated PECs and TDMs, the adiabatic transition parameters, including the Franck-Condon factors (FCFs) and radiative lifetimes for spin-forbidden transitions (a(3)Pi(0+,1) -X-1 Sigma(+)(0+) and A(1)Pi(1)-a(3)Pi(0+,1)), are determined. As for the a(3)Pi(0+,1) -X-1 Sigma(+)(0+) transition, the radiative lifetimes are shorter, which means the stronger emission could occur. The FCFs for the A(1)Pi(1)-a(3)Pi(0+,1) transition are highly diagonal and the values are greater than 0.94, but with large vibrational radiative lifetimes. The results obtained in this work are consistent with experimental ones and can be used to further investigate the mechanism of chemical reaction dynamics. (C) 2020 Elsevier Ltd. All rights reserved.