Loss of Ultracold <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mmultiscripts><mml:mrow><mml:mi>Rb</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>87</mml:mn></mml:mrow></mml:mmultiscripts><mml:mmultiscripts><mml:mrow><mml:mi>Cs</mml:mi></mml:mrow><mml:mprescripts/><mml:none/><mml:mrow><mml:mn>133</mml:mn></mml:mrow></mml:mmultiscripts></mml:mrow></mml:math> Molecules via Optical Excitation of Long-Lived Two-Body Collision Complexes
Philip D. Gregory, Jacob A. Blackmore, Sarah Bromley, Simon L. Cornish
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.