Loss of ultracold RbCs molecules via optical excitation of long-lived two-body collision complexes
Abstract
We show that the lifetime of ultracold ground-state 87Rb133Cs 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 0.530.06 ms in the dark. We find that the rate of optical excitation of the collision complex is 3+4-2×103 W-1 cm2 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.
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