Prospects for laser cooling TlF

Abstract

We measure the upper-state lifetime and two ratios of vibrational branching fractions ${f}_{{v}^{\ensuremath{'}}v}$ on the $B{\phantom{\rule{0.16em}{0ex}}}^{3}{\ensuremath{\Pi}}_{1}({v}^{\ensuremath{'}})\ensuremath{-}X{\phantom{\rule{0.16em}{0ex}}}^{1}{\ensuremath{\Sigma}}^{+}(v)$ transition of TlF. We find the $B$-state lifetime to be 99(9) ns. We also determine that the off-diagonal vibrational decays are highly suppressed: ${f}_{01}/{f}_{00}<2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and ${f}_{02}/{f}_{00}=1.10(6)$%, in excellent agreement with their predicted values of ${f}_{01}/{f}_{00}<8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ and ${f}_{02}/{f}_{00}=1.0(2)$% based on Franck-Condon factors calculated using Morse and Rydberg-Klein-Rees (RKR) potentials. The implications of these results for the possible laser cooling of TlF and fundamental symmetries experiments are discussed.