High-sensitivity Franck-condon Factor Measurements Enabled By Optical Cycling

Recent experiments have successfully laser cooled a variety of molecules, including diatomic, linear triatomic, and symmetric top species [1-3]. Laser cooling and trapping can require repeatedly scattering more than 10,000 photons per molecule, so all potential losses above the level of 1 part in 10$^{5}$ must be identified and repumped to mitigate losses. Here, we report on the use of optical cycling to measure vibrational branching ratios of laser-coolable polyatomic molecules. We achieve relative intensity sensitivities at the 10$^{-5}$ level, approximately a factor of 100 more sensitive than previous dispersed fluorescence studies [4-6]. The apparatus described can be adapted to probe any molecule with a nearly-closed cycling transition by tuning two laser wavelengths. In addition, we discuss how these high-precision branching ratio measurements have allowed us to infer values for Renner-Teller parameters in CaOH and YbOH, and for pseudo-Jahn-Teller parameters in CaOCH$_3$. [1] J. Barry, et al., Nature 512, 286 (2014). [2] I. Kozyryev, et al., Phys. Rev. Lett. 118, 173201 (2017). [3] D. Mitra, N. B. Vilas, et al., Science 369, 1366 (2020). [4] I. Kozyryev, et al., New J. Phys. 21, 052002 (2019). [5] A. C. Paul, et al., J. Chem. Phys. 151, 134303 (2019). [6] E. T. Mengesha, et al., J. Phys. Chem. A 124, 3135 (2020)

BRANCHING RATIOS, RADIATIVE LIFETIMES, AND TRANSITION DIPOLE MOMENTS FOR YbOH

Yb-containing molecules exhibit strongly enhanced sensitivity to physics beyond the Standard Model, including the symmetry-violating electron electric dipole moment (eEDM). Laser cooling and trapping are necessary in order to fully leverage this intrinsic sensitivity. To this end, we present medium resolution laser-induced fluorescence (LIF) excitation spectra of a rotationally cold sample of YbOH in the 17300-17950 cm$^{-1}$ range recorded using two-dimensional (excitation and dispersed fluorescence) spectroscopy. High resolution dispersed LIF (DLIF) spectra and radiative lifetimes of numerous bands detected in the medium resolution spectra are described. The vibronic energy levels of the \tilde{X} \, ^2\Sigma^{+} state are predicted using a discrete variable representation approach and compared with observations. The DLIF spectra are analyzed to determine vibrational branching ratios and transition dipole moments, important determinants in the efficacy of laser cooling. Implications for laser cooling and trapping of YbOH are discussed

Λ\Lambda-Enhanced Imaging of Molecules in an Optical Trap

We report non-destructive imaging of optically trapped calcium monofluoride (CaF) molecules using in-situ $\Lambda$-enhanced gray molasses cooling. $200$ times more fluorescence is obtained compared to destructive on-resonance imaging, and the trapped molecules remain at a temperature of $20\,\mu\text{K}$. The achieved number of scattered photons makes possible non-destructive single-shot detection of single molecules with high fidelity.Comment: 6 pages, 4 figure

Radio Frequency Magneto-Optical Trapping of CaF with High Density

We demonstrate significantly improved magneto-optical trapping of molecules using a very slow cryogenic beam source and RF modulated and DC magnetic fields. The RF MOT confines $1.1(3) \times 10^5$ CaF molecules at a density of $4(1) \times 10^6$ cm$^{-3}$, which is an order of magnitude greater than previous molecular MOTs. Near Doppler-limited temperatures of $340(20)$ $\mu$K are attained. The achieved density enables future work to directly load optical tweezers and create optical arrays for quantum simulation.Comment: 5 Pages, 4 Figure

One dimensional magneto-optical compression of a cold CaF molecular beam

We demonstrate with a RF-MOT the one dimensional, transverse magneto-optical compression of a cold beam of calcium monofluoride (CaF). By continually alternating the magnetic field direction and laser polarizations of the magneto-optical trap, a photon scattering rate of $2\pi \times$0.4 MHz is achieved. A 3D model for this RF-MOT, validated by agreement with data, predicts a 3D RF-MOT capture velocity for CaF of 5 m/s