Saturation of ${\mathrm{Cs}}_2$ photoassociation in an optical dipole trap

We present studies of strong coupling in single-photon photoassociation of cesium dimers using an optical dipole trap. A thermodynamic model of the trap depletion dynamics is employed to extract absolute rate coefficents. From the dependence of the rate coefficient on the photoassociation laser intensity, we observe saturation of the photoassociation scattering probability at the unitarity limit in quantitative agreement with the theoretical model by Bohn and Julienne [Phys. Rev. A 60, 414 (1999)]. Also the corresponding power broadening of the resonance width is measured. We could not observe an intensity-dependent light shift in contrast to findings for lithium and rubidium, which is attributed to the absence of a $p$- or $d$-wave shape resonance in cesium.

Figure 1

Overview of the important potential energy curves for the photoassociation of cesium molecules.

Figure 2

Upper panels: trap loss spectra of the studied photoassociation resonance $v=6$, $J=2$ of the $0_g^{-}$ outer well for different laser intensities. Lower panels: spectra of the photoassociation rate coefficients extracted from the trap loss signal. The solid lines represent Lorentzian fits to the resonances.

Figure 3

Photoassociation scattering probability (upper panel), resonance width (middle panel), and resonance line shift (lower panel) as a function of the photoassociation laser intensity. The solid lines represent the fit to the saturation model of Bohn and Julienne.