Characterization of the A²Π_1/2(0,0,0) and X²Σ⁺(0,0,0) states of ¹⁷¹YbOH and ¹⁷³YbOH

The odd isotopologues of ytterbium monohydroxide, ^171,173YbOH, have been identied as promising molecules in which to measure parity (P) and time reversal (T) violating physics. We report on the characterization of the A²Π_1/2(0,0,0)-X²Σ⁺(0,0,0) band near 577 nm for ^171,173YbOH, a prerequisite to searches for P and T-violating physics with these molecules. Both laser-induced fuorescence (LIF) excitation spectra of a supersonic molecular beam sample and absorption spectra of a cryogenic buffer-gas cooled sample were recorded. Additionally, a novel spectroscopic technique based on laser-enhanced chemical synthesis is demonstrated and utilized in the absorption measurements. This technique was critical as it enabled the disentangling of the congested isotopologue structure. An effective Hamiltonian model is used to extract the fine and hyperfine parameters for the A²Π_1/2(0,0,0) and X²Σ⁺(0,0,0) states. The determined X²Σ⁺(0,0,0) hyperfine parameters are consistent with recently predicted values¹. Our analysis provides experimental confirmation of the computational methods used to compute the P,T-violating coupling constants, W_d and W_M, theoretical constants which correlate P,T-violating physics to P,T-violating energy shifts in the molecule. The mass and magnetic moment dependence of the fine and hyperfine parameters for all isotopologues for both the A²Π_1/2(0,0,0) and X²Σ⁺(0,0,0) states for YbOH and isoelectronic YbF are discussed.

¹M. Denis et al, J. Chem. Phys. 152, 084303 (2020), K. Gaul and R. Berger, Phys. Rev. A 101, 012508 (2020), J. Liu et al, J. Chem. Phys. 154, 064110 (2021)