Theoretical Investigation of CaH Formation in a Buffer Gas Cell

Calcium monohydride (CaH) has proved to be a viable candidate for laser cooling and was justified for further study as a potential pathway to produce ultracold hydrogen [1]. Efficient formation of CaH is non-trivial, and the current method for doing so is via laser ablation of solid CaH2 [2]. However, CaH formation through a chemical reaction in a buffer gas cell leads to a more stable CaH production and thus a more desirable experimental protocol. In this work, we calculate the rate of CaH formation when Ca atoms are scattered with H2 molecules, and its dependence on initial H2 rovibrational energies. A quasi-classical trajectory (QCT) method is used to simulate these trajectories [3], and CaH formation rates are calculated as a function of collision energy and initial rovibrational state of H2. As a result, we find that it could be beneficial to excite H2 to higher vibrational states via an intermediate electronic state to boost the production of CaH molecules. These results may serve as experimental motivation for the efficient formation of CaH for further study.

[1] - S F Vázquez-Carson et al 2022 New J. Phys. 24 083006

[2] - Weinstein, J., deCarvalho, R., Guillet, T. et al. Magnetic trapping of calcium monohydride molecules at millikelvin temperatures. Nature 395, 148–150 (1998). https://doi.org/10.1038/25949

[3] - J. Pérez-Ríos, An Introduction to Cold and Ultracold Chemistry (Springer International Publishing, New York, 2020)