Photoassociation inside an optical dipole trap: absolute rate coefficients and Franck–Condon factors

We present quantitative measurements of the photoassociation of cesium molecules inside a far-detuned optical dipole trap. A model of the trap-depletion dynamics is derived which allows us to extract absolute photoassociation rate coefficients for the initial single-photon photoassociation step from measured trap-loss spectra. The sensitivity of this approach is demonstrated by measuring the Franck–Condon modulation of the weak photoassociation transitions into the low-vibrational levels of the outer well of the Og- state that correlates to the 6s+6p3/2 asymptote. The measurements are compared to theoretical predictions. In a magneto-optical trap, these transitions have previously only been observed indirectly through ionization of ground-state molecules.