Eustace Edwards

Since the the idea of laser cooling on thallium fluoride’s (TlF) |X¹∑> → |B³∏> optical transition, there has been renewed interest TlF beams for both laser cooling and fundamental symmetry test. In particular, researchers were interested in the hyperfine structure in the lowest rotational energy levels of the B state, and the laser cooling potential of lowest Q-branch transition. In this work, we constructed and characterized a cryogenic buffer gas beam source (CBGBS) to produce a rotationally cold TlF beam (3.6K). Using the cold beam, we recorded low temperature hyperfine spectrum, and discovered the B state possesses hyperfine interaction (roughly 4 times the size of the rotational constant), which leads to rotational state mixing, and spoiling of the initially proposed laser cooling transition. Since the cold beam provided unambiguous identification of TlF’s Q branch transitions, we were able to perform preliminary transverse laser cooling on the proposed laser cooling transitions.