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M. A. BELLOS, D. RAHMLOW, R. CAROLLO, J. BANERJEE, E. E. EYLER, P. L. GOULD AND W. C. STWALLEY, Department of Physics, University of Connecticut, Storrs, CT 06269.

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 ⁸⁵Rb atoms in a MOT were photoassociated to levels of the 1 ³ _g state a few hundred wavenumbers above the 5S+5P_3/2 limit. These transitions were found to be strong even though they occur at short internuclear separations (R_e=10 a₀). Levels of the 1 ³ _g state spontaneously decay to the a ³ _u⁺ state, where they are detected by resonantly enhanced multiphoton ionization with time-of-flight spectroscopy. We have observed most vibrational levels of the 1 ³ _g state belonging to all of its spin-orbit components (0_g⁺,0_g^-,1_g,2_g). Recent unpublished ab-initio calculations [2] of these potentials show good agreement with the observed vibrational and rotational constants. This work is supported by the NSF, AFOSR, and UConn Research Foundation.

[1] M.-L. Almazor et. al. , Eur. Phys. J. D \textbf15 355 (2001)

[2] O. Dulieu, private communication