High resolution laser excitation spectra and the Franck-Condon factors of the A 2 Π-X 2 Σ + electronic transition of MgF

Magnesium monofluoride (MgF) is proposed as an ideal candidate radical for direct laser cooling. Here, the high resolution laser excitation spectra of MgF for the A2Π-X2Σ+ electronic transition system were recorded by using laser induced fluorescence (LIF) technique. The MgF radicals are produced by discharging SF6/Ar gas mixtures between the tips of two magnesium needles in a supersonic jet expansion. We recorded 19 vibrational bands in total belonging to three sequences of Δv=0, ±1 in the region of 348-370 nm. Accurate spectroscopic constants for both A2Π and X2Σ+ states are determined from rotational analysis of the experimental spectra. Spectroscopic parameters, including the Franck-Condon factors (FCFs), are determined from the experimental results and the Rydberg-Klein-Rees (RKR) calculations. Significant discrepancies between the experimentally measured and RKR-calculated FCFs are found, indicating that the FCFs are nearly independent on the spin-orbit coupling in the A2Π state. Potential energy curves (PECs) and Franck-Condon factors (FCFs) determined here provide necessary data for the theoretical simulation of the laser-cooling scheme of MgF.