Knowledge Bank

The low-lying $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta 1$ state of ThF$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ has advantageous properties for studies of the electron electric dipole moment. Calculations indicate that internal fields as high as 90 GV/cm can be generated, and there is just one isotope of ThF with significant natural abundance. Previous experiments show two low-lying electronic states of ThF$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ spaced by 315 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ (JCP 136, 104305 (2012)). These are $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}\Sigma$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}\Delta 1$, but the ordering is still in question. Experiments are in progress to determine the electronic angular momentum of the ground state. Laser excitation spectra for ThF$\mathrm{<mrow\; data-mjx-texclass="ORD">+</mrow>}$ have been recorded for transitions in the 19300-21100 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ range. For eEDM studies it is technically more convenient to work with lower energy transitions. Survey spectra covering the range 15000-19000 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ are currently being recorded. Results from these measurements will be presented and their relevance to possible eEDM studies will be discussed.