Laser-induced fluorescence detection of 205TlF for a nuclear Schiff moment measurement

The Cold Molecule Nuclear Time-Reversal Experiment (CeNTREX) aims to measure the time-reversal-symmetry–violating nuclear Schiff moment of 205Tl. A cryogenic beam of TlF molecules undergoes nuclear magnetic resonance in an applied electric field using the Ramsey method of separated oscillatory fields. An additional spin-precession phase arises from the interaction between the Schiff moment and the electric field. The phase information is transformed into a population imbalance between two nuclear spin states. To enable state-resolved detection of these states, which are not resolvable with an optical transition in TlF, one spin population is coherently transferred to a different rotational state. The rotational state populations are then measured quasi-simultaneously, via laser-induced fluorescence (LIF), by rapid switching between two detection lasers. The statistical sensitivity of the measurement is limited by detection efficiency, fluctuations in background laser light scattering, and velocity-dependent effects associated with semi-closed optical cycling transitions. The latter two effects can introduce excess apparent phase noise beyond the shot-noise limit. In this talk, we present the LIF detector design and calibration for CeNTREX, along with detection strategies aimed at maximizing signal-to-noise ratio and phase sensitivity.