Optical cycling of thallium fluoride

Investigations of optical cycling of the B³Π₁(ν′ = 0) ← X¹Σ⁺(ν = 0) transition of thallium fluoride are reported. These investigations are motivated by the promise TlF holds for a measurement of the nuclear electric-dipole moment. With the goal of discovering a robust optical cycling scheme we measure UV fluorescence from the laser excitation of a cryogenic molecular beam and compare those results to theoretical predictions. A simple theoretical model which considers only rotational branching fails to agree with experiment as polarization and hyperfine dark states of the ground state are found to dramatically reduce photon cycling rates compared to those of a simple two-level system. More complete quantum mechanical trajectory simulations are reported which better capture the reality of the experiment and the effects of these dark states.