Vibrational branching ratios and hyperfine structure of $^{11}$BH and its suitability for laser cooling

TL;DR

This study demonstrates that $^{11}$BH molecules have highly favorable vibrational branching ratios and hyperfine structures, making them excellent candidates for laser cooling, trapping, and manipulation in quantum experiments.

Contribution

The paper provides detailed measurements of vibrational branching ratios, hyperfine structures, and transition frequencies for $^{11}$BH, establishing its suitability for laser cooling applications.

Findings

Branching ratios favor laser cooling of BH.

Hyperfine structure characterized for relevant states.

Small spin-forbidden transition probability confirmed.

Abstract

The simple structure of the BH molecule makes it an excellent candidate for direct laser cooling. We measure the branching ratios for the decay of the ${\rm A}^{1}\Pi (v'=0)$ state to vibrational levels of the ground state, ${\rm X}^{1}\Sigma^{+}$, and find that they are exceedingly favourable for laser cooling. We verify that the branching ratio for the spin-forbidden transition to the intermediate ${\rm a}^{3}\Pi$ state is inconsequentially small. We measure the frequency of the lowest rotational transition of the X state, and the hyperfine structure in the relevant levels of both the X and A states, and determine the nuclear electric quadrupole and magnetic dipole coupling constants. Our results show that, with a relatively simple laser cooling scheme, a Zeeman slower and magneto-optical trap can be used to cool, slow and trap BH molecules.