Vibrational Branching Ratios of Low-Symmetry Strontium-Containing Molecules

Recent advances in direct laser cooling of linear polyatomic molecules promise advances in quantum information, cold chemistry, and precision measurement experiments [1-3]. Larger and less-symmetric molecules have several additional features. However, the pathway to laser cooling low-symmetry species, such as asymmetric tops, is not yet fully known. Although 1-D laser cooling of symmetric tops works [4], and proposals for laser cooling of asymmetric tops have been published [3], the effect of rotational perturbations and vibrational branching on full laser cooling of low symmetry species is not well understood. To study quantitatively how symmetry affects laser cooling, we present here vibrational branching ratio measurements of strontium-containing molecules from three different symmetry classes. By measuring the vibrational branching ratios of these molecules to the 0.01-0.1% level, we assess one aspect of the viability of laser cooling these species in the future. Additionally, we compare our results to isostructural calcium-containing species to illuminate how the combination of mass and structural complexity can affect laser cooling of low-symmetry molecules more generally.

[1] Albert et al, Phys. Rev. X 10 2020

[2] Kozyryev, Hutzler, Phys. Rev. Lett. 119 2017

[3] Augenbraun et al, Phys. Rev. X 10 2020

[4] Mitra et al, Science 369 2020