arXiv:2002.04431 · Physical Review Letters

Loss of Ultracold Rb 87 Cs 133 Molecules via Optical Excitation of Long-Lived Two-Body Collision Complexes

Philip D. Gregory, Jacob A. Blackmore, Sarah Bromley, Simon L. Cornish

Published Apr 23, 2020• 110 citations

Abstract

We show that the lifetime of ultracold ground-state ^{87}Rb^{133}Cs molecules in an optical trap is limited by fast optical excitation of long-lived two-body collision complexes. We partially suppress this loss mechanism by applying square-wave modulation to the trap intensity, such that the molecules spend 75% of each modulation cycle in the dark. By varying the modulation frequency, we show that the lifetime of the collision complex is 0.53±0.06 ms in the dark. We find that the rate of optical excitation of the collision complex is 3_{-2}^{+4}×10^{3} W^{-1} cm^{2} s^{-1} for λ=1550 nm, leading to a lifetime of <100 ns for typical trap intensities. These results explain the two-body loss observed in experiments on nonreactive bialkali molecules.

DOI: 10.1103/physrevlett.124.163402

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