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arXiv · 1803.04849

Quantitative theoretical analysis of lifetimes and decay rates relevant in laser cooling BaH

Keith Moore·Ian C Lane
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Abstract

Tiny radiative losses below the 0.1% level can prove ruinous to the effective laser cooling of a molecule. In this paper the laser cooling of a hydride is studied with rovibronic detail using ab initio quantum chemistry in order to document the decays to all possible electronic states (not just the vibrational branching within a single electronic transition) and to identify the most populated final quantum states. The effect of spin-orbit and associated couplings on the properties of the lowest excited states of BaH are analysed in detail. The lifetimes of the A$^2Π_{1/2}$, H$^2Δ_{3/2}$ and E$^2Π_{1/2}$ states are calculated (136 ns, 5.8 μs and 46 ns respectively) for the first time, while the theoretical value for B$^2Σ^+_{1/2}$ is in good agreement with experiments. Using a simple rate model the numbers of absorption-emission cycles possible for both one- and two-colour cooling on the competing electronic transitions are determined, and it is clearly demonstrated that the A$^2Π$ - X$^2Σ^+$ transition is superior to B$^2Σ^+$ - X$^2Σ^+$, where multiple tiny decay channels degrade its efficiency. Further possible improvements to the cooling method are proposed.

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BibTeXRIS

Keith Moore, Ian C Lane. 2018-03-15. Quantitative theoretical analysis of lifetimes and decay rates relevant in laser cooling BaH. https://doi.org/10.1016/j.jqsrt.2018.03.003

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