Cold CH radicals for laser cooling and trapping

Abstract

Ultracold CH radicals promise a fruitful testbed for probing quantum-state controllable organic chemistry. In this work, we calculate CH vibrational branching ratios (VBRs) and rotational branching ratios (RBRs) with ground state mixing. We subsequently use these values to inform optical cycling proposals and consider two possible radiative cooling schemes using the $X^2\Pi \leftarrow A^2\Delta$ and $X^2\Pi \leftarrow B^2{\Sigma }^{-}$ transitions. As a first step towards laser cooled CH, we characterize the effective buffer gas cooling of this species and produce $\sim 5\times 10^{10}$ CH molecules per pulse with a rotational temperature of 2(1) K and a translational temperature of 7(2) K. We also determine the CH-helium collisional cross section to be $2.4(8)\times 10^{-14}$ cm${}^2$. This value is crucial to correctly account for collisional broadening and accurately extract the in-cell CH density. These cold CH molecules mark an ideal starting point for future laser cooling and trapping experiments and tests of cold organic chemistry.

arXiv comment17 pages, 5 figures

References in corpus (24)

• A High Phase-Space-Density Gas of Polar Molecules
• Cold and Ultracold Molecules: Science, Technology, and Applications
• Laser cooling of a diatomic molecule
• Magneto-optical trapping of a diatomic molecule
• The Buffer Gas Beam: An Intense, Cold, and Slow Source for Atoms and Molecules
• Radio Frequency Magneto-Optical Trapping of CaF with High Density
• 3-D Magneto-Optical Trap of Yttrium Monoxide
• Radiative force from optical cycling on a diatomic molecule
• Magneto-Optical Trap for Polar Molecules
• Destabilization of dark states and optical spectroscopy in Zeeman-degenerate atomic systems
• Optoelectrical cooling of polar molecules to sub-millikelvin temperatures
• A search for varying fundamental constants using Hz-level frequency measurements of cold CH molecules
• Molecular Asymmetry and Optical Cycling: Laser Cooling Asymmetric Top Molecules
• Characteristics of a magneto-optical trap of molecules
• Laser cooling of new atomic and molecular species with ultrafast pulses
• Laser cooling with ultrafast pulse trains
• Magnetic Trapping of Cold Methyl Radicals
• Lifetime of the A(v'=0) state and Franck-Condon factor of the A-X(0-0) transition of CaF measured by the saturation of laser-induced fluorescence
• $\Lambda$-doublet spectra of diatomic radicals and their dependence on fundamental constants
• Prospects for rapid deceleration of small molecules by optical bichromatic forces
• Establishing a nearly closed cycling transition in a polyatomic molecule
• Principles and design of a Zeeman-Sisyphus decelerator for molecular beams
• Bright, continuous beams of cold free radicals
• Fine- and hyperfine-structure effects in molecular photoionization: I. General theory and direct photoionization

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