Electronic spectroscopy and ionization potentials for YbOH and YbOCH3

The polyatomic molecules YbOH and YbOCH3 have been recognized as being of potential value for spectroscopic experiments that explore charge-parity and time-reversal symmetry violation effects. These measurements require very high precision, which, in turn, will necessitate that the molecules be manipulated at ultracold temperatures. Both YbOH and YbOCH3 have electronic transitions that appear suitable for laser cooling ((A) over tilde (2)Pi(1/2)-(X) over tilde (2)Sigma(+) and (A) over tilde E-2(1/2)-(X) over tilde (2)A(1), respectively) but the currently available spectroscopic data are not sufficient to determine the extent to which population leaks may compromise the optical cooling processes. A further complication is that the quantum states of interest for these measurements will need to be selectively populated. The (A) over tilde-(X) over tilde band systems of both YbOH and YbOCH3 show evidence of vibronic perturbations, such that there are unassigned vibronic features at energies that are just above the origin bands. In the present study we have recorded spectra for the (A) over tilde (2)Pi(1/2)-(X) over tilde (2)Sigma(+) transition of jet-cooled YbOD to facilitate the vibronic assignments. In addition, spectra for the (B) over tilde (2)Sigma(+)-(X) over tilde (2)Sigma(+) transition of YbOH were recorded, establishing the origin band at 20473.8 cm(-1). Previously, the reaction of Yb with CH3OH has been used to generate gas-phase YbOCH3. As this reaction also yields YbOH, there have been complications in spectroscopic studies of YbOCH3 due to overlap of the (A) over tilde-(X) over tilde band systems. To identify specific regions of overlap, resonantly enhanced two-photon ionization spectra were recorded using mass-resolved detection of the YbOH+ and YbOCH3+ ions. These data confirmed the overlap of vibronic bands near 17 640 and 17 680 cm(-1). Two-photon ionization spectroscopy also provided accurate ionization energies (IE), IE(YbOH) = 45 788(10) and IE(YbOCH3) = 45 283(10) cm(-1). The IE for YbOH is relevant to problems encountered in previous attempts to determine the bond-dissociation energy of YbOH+.

Automated summary

The polyatomic molecules YbOH and YbOCH3 have potential value for spectroscopic experiments exploring symmetry violation effects. Manipulating these molecules at ultracold temperatures is required for high precision measurements. Spectra of YbOD and YbOH were recorded to assign vibrational levels and confirm overlapping bands.