A cold, slow beam of TlF molecules for an improved probe for the nuclear Schiff moment

We present a new experimental effort to search for the nuclear Schiff moment (SM) using thallium fluoride (TlF) molecules. Our approach capitalizes on the strong internal electric field present in a polarized molecule to amplify the effect of the SM. We project a 25-fold improvement over the current state of the art sensitivity to certain underlying mechanisms such as the CP-violating QCD $\theta $-parameter [1]. Our recent measurements indicate that optical cycling is possible on the $X^{\mathrm{1}}\Sigma ^{\mathrm{+}}\to B^{\mathrm{3}}\Pi_{\mathrm{1}}$ electronic transition of TlF [2]. Here a single laser will enable 100 photons to be scattered before an excited vibrational level is populated. This is sufficient for unit-efficiency fluorescence detection, rotational cooling, and state preparation. With a single repump laser, \textasciitilde 10$^{\mathrm{4}}$ photons could be scattered, sufficient for transverse laser cooling that could substantially increase the brightness of the molecular beam. We report on the production of a cold and slow beam of TlF molecules from a cryogenic buffer gas beam source and present flux measurements for a range of TlF vaporization techniques. We also present our progress towards understanding the hyperfine structure in the $B^{\mathrm{3}}\Pi_{\mathrm{1}}$ state and its role in optical cycling. [1] B. Graner, Y. Chen, E. G. Lindahl, and B.R. Heckel, Reduced limit on the Permanent Electric Dipole Moment of $^{\mathrm{199}}$Hg, arXiv:1601.04339. [2] L. R. Hunter, S. K. Peck, A. S. Greenspon, S. Saad Alam, and D. DeMille, Prospects for laser cooling TlF, \textit{Phys. Rev. A}, \textbf{85}, 012511 (2012).