Experiment to search forP- andT-violating interactions in the hyperfine structure of thallium fluoride

The authors describe a molecular-beam-resonance experiment to search for $P$- and $T$-violating interactions in the thallium fluoride molecule. Specifically the interactions looked for are of the form ${\mathcal{H}}_{\mathrm{PT}}=d{\hat{\sigma }}_{\mathrm{Tl}}·{\hat{\lambda }}_{\mathrm{TlF}}$, where $d$ is a coupling constant, ${\hat{\sigma }}_{\mathrm{Tl}}$ is a unit vector parallel to the spin angular momentum of the thallium nucleus, and ${\hat{\lambda }}_{\mathrm{TlF}}$ is a unit vector along the internuclear axis. The null result of the experiment is $\frac{d}{h}=11\mathrm{}\pm 42$ mHz. This result implies new upper limits on the electric dipole moment of the proton and on a possible weak, $P$- and $T$-violating, neutral-current tensor interaction.