Prospects for laser cooling TlF

We measure the upper-state lifetime and two ratios of vibrational branching fractions $f_{v^{\prime }v}$ on the $B{}^3{\Pi }_1\left(v^{\prime }\right)-X{}^1{\Sigma }^{+}\left(v\right)$ 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: $f_{01}/f_{00}<2\times {10}^{-4}$ and $f_{02}/f_{00}=1.10\left(6\right)$%, in excellent agreement with their predicted values of $f_{01}/f_{00}<8\times {10}^{-4}$ and $f_{02}/f_{00}=1.0\left(2\right)$% 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.