Electronic spectroscopy and ionization potentials for YbOH and YbOCH3

Abstract

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 ultra-cold temperatures. Both YbOH and YbOCH3 have electronic transitions that appear suitable for laser cooling (𝐴 " 2 P1/2-𝑋 $ 2 S + and 𝐴 " 2 E1/2-𝑋 $ 2 A1, respectively) but the currently available spectroscopic data is 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 " − 𝑋 $ 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 " 2 P1/2-𝑋 $ 2 S + transition of jetcooled YbOD to facilitate the vibronic assignments. In addition, spectra for the 𝐵 $ 2 S + -𝑋 $ 2 S + 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 " − 𝑋 $ 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 17640 and 17680 cm -1 . Two-photon ionization spectroscopy also provided accurate ionization energies of IE(YbOH)=45788(10) and IE(YbOCH3)=45283(10) cm -1 . The IE for YbOH is relevant to problems encountered in previous attempts to determine the bond dissociation energy of YbOH + .