Direct laser cooling of calcium monohydride molecules

Abstract

We demonstrate optical cycling and sub-Doppler laser cooling of a cryogenic buffer-gas beam of calcium monohydride (CaH) molecules. We measure vibrational branching ratios for laser cooling transitions for both excited electronic states A and B. We measure further that repeated photon scattering via the $A\leftarrow X$ transition is achievable at a rate of $\sim$ $1.6\times 10^6$ photons/s and demonstrate the interaction-time limited scattering of $\sim$ $200$ photons by repumping the largest vibrational decay channel. We also demonstrate the ability to sub-Doppler cool a molecular beam of CaH through the magnetically assisted Sisyphus effect. Using a standing wave of light, we lower the molecular beam's transverse temperature from $12.2(1.2)$ mK to $5.7(1.1)$ mK. We compare these results to sub-Doppler forces modeled using optical Bloch equations and Monte Carlo simulations of the molecular beam trajectories. This work establishes a clear pathway for creating a magneto-optical trap (MOT) of CaH molecules. Such a MOT could serve as a starting point for production of ultracold hydrogen gas via dissociation of a trapped CaH cloud.

11 pages, 4 figures, 3 tables

References in corpus (9)

• Many-Body Physics with Ultracold Gases
• Magneto-optical trapping of a diatomic molecule
• Radio Frequency Magneto-Optical Trapping of CaF with High Density
• Sisyphus Cooling of Electrically Trapped Polyatomic Molecules
• Magneto-Optical Trap for Polar Molecules
• Laser cooling of molecules
• Three-dimensional Doppler, polarization-gradient, and magneto-optical forces for atoms and molecules with dark states
• Spectroscopy of atomic hydrogen. How is the Rydberg constant determined?
• Determination of CaOH and CaOCH${}_3$ vibrational branching ratios for direct laser cooling and trapping

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