Radiative Branching Ratios for Excited States of $^{174}$YbF:   Application to Laser Cooling
  We excite YbF molecules to low-lying vibrational levels of the $A^2\Pi_{1/2}$ state, and of the nearby perturber state sometimes called [18.6]0.5. By dispersing the fluorescence, we measure branching ratios for the radiative decay to vibrational levels of the $X^2\Sigma^+$ state. These ratios help to determine the optimum laser cooling scheme for the molecule. Our results establish the practicality of a scheme that was previously suggested [Tarbutt et al., New J. Phys. 15 (2013) 053034] and show how the scheme can be modified to provide a stronger radiative cooling force. 
I.J. Smallman, F. Wang, T.C. Steimle, M.R. Tarbutt, E.A. Hinds
physics.atom-ph