Accurate \textit{ab initio} calculations of RaF electronic structure indicate the need for more laser-spectroscopical measurements

Abstract

Recently a breakthrough has been achieved in laser-spectroscopic studies of short-lived radioactive compounds with the first measurements of the radium monofluoride molecule (RaF) UV/vis spectra. We report results from high accuracy \emph{ab initio} calculations of the RaF electronic structure for ground and low-lying excited electronic states. Two different methods agree excellently with experimental excitation energies from the electronic ground state to the $^2\Pi_{1/2}$ and $^2\Pi_{3/2}$ states, but lead consistently and unambiguously to deviations from experimental-based adiabatic transition energy estimates for the $^2\Sigma_{1/2}$ excited electronic state and show that more measurements are needed to clarify spectroscopic assignment of the $^2\Delta$ states.