Theoretical study of Properties of Radium Monofluoride

Heavy diatomic molecules are currently considered to be among the most sensitive systems used in the search for the eEDM and in probing of the Standard Model of particle physics. In certain molecules effects resulting from both parity violation and time-reversal violation (P,T- odd effects) are considerably enhanced with respect to atomic systems. The strength of these interactions grows with atomic number, nuclear spin and nuclear deformation. RaF is of particular interest because it is predicted to have an electronic structure appropriate for laser cooling and also being sensitive to the new phenomena\footnote{L.V. Skripnikov. J. Chem. Phys. 153, 114114, 2020}. The suitability of RaF for laser-cooling depends critically on its energy levels structure, lifetimes of its excited states, vibrational branching ratios and electronic transition probabilities. Although experimental knowledge of radioactive molecules is scarce, a recent work\footnote{R.F. Garcia Ruiz et al. Nature, 581, 396-400, 2020} presented an approach for performing laser spectroscopy of short-lived radioactive molecules, using the highly sensitive collinear resonance ionization method. As an example of the novel technique RaF was used. This work aims to determine properties at the highest possible level of computational accuracy, following the procedure from our earlier work\footnote{Y. Hao et al. J. Chem . Phys. 151, 034302, 2019}, to conclude on the suitability of RaF for laser-cooling and compare with existing experimental data. We present high-accuracy relativistic Fock-Space coupled cluster calculations of the potential energy curves and the spectroscopic constants of the ground state and the lower excited states of RaF. The ionization potential of RaF was calculated and the Franck-Cordon factors were obtained, based on calculated potential energy curves. We have also calculated the TDMs of different transitions using multireference configuration interaction approach. Based on defined TDMs and experimental transitions, lifetimes of the excited states in RaF were determined. The new results are compared with existing theoretical and experimental data