Knowledge Bank

We report on the observation of blue-detuned photoassociation as proposed in [1] and references therein. "Blue-detuned" refers to the location of vibrational levels --- energetically above the corresponding atomic asymptote. Ultracold $\mathrm{<mrow\; data-mjx-texclass="ORD">85</mrow>}$Rb atoms in a MOT were photoassociated to levels of the $13\Pi g$ state a few hundred wavenumbers above the $5S+5P3/2$ limit. These transitions were found to be strong even though they occur at short internuclear separations ($Re$=$10a0$). Levels of the $13\Pi g$ state spontaneously decay to the $a3\Sigma u+$ state, where they are detected by resonantly enhanced multiphoton ionization with time-of-flight spectroscopy. We have observed most vibrational levels of the $13\Pi g$ state belonging to all of its spin-orbit components ($0g+,0g-,1g,2g$). Recent unpublished \emph{ab-initio} calculations [2] of these potentials show good agreement with the observed vibrational and rotational constants. \ [1] M.-L. Almazor \emph{et. al.}, \emph{Eur. Phys. J. D} \textbf{15} 355 (2001) [2] O. Dulieu, private communication