Theoretical study of laser cooling of magnesium monofluoride using ab initio methods

摘要

A theoretical investigation of the feasibility of laser-cooling the (MgF)-Mg-24-F-19 molecule is performed using ab initio calculations. The low-lying electronic states are determined by the multireference configuration-interaction (MRCI) method, where the Davidson modification (+Q) with the Douglas-Kroll-Hess scalar relativistic correction is also taken into account. The calculated spectroscopic constants are in excellent agreement with the available experimental data. The Franck-Condon factors (FCFs), radiative lifetimes, and radiative widths are verified by calculating the potential energy curves and the transition dipole moment of the A(2)Pi(nu') -> X-2 Sigma(+)(nu) transition. Our calculation indicates that the A(2)Pi(nu' = 0) -> X-2 Sigma(+) (nu = 0) transition provides highly diagonally distributed FCFs (f(00) = 0.917) and a short radiative lifetime (tau = 7.96 ns) for the A(2)Pi(nu' = 0) state, which is short enough for rapid laser cooling. The required cooling wavelengths are in the ultraviolet region. A comprehensive scheme demonstrates the possibility of laser-cooling MgF. Moreover, the C-2 Sigma(+) state is confirmed to be a Rydberg state at the MRCI level, which is in line with experimental conjecture. The B-2 Pi and D-2 Sigma(+) states are also reported, but they have not been observed to date.