30min:

WILLIAM C. STWALLEY, Department of Physics, University of Connecticut, Storrs, CT 06269-3046.

The field of laser cooling and trapping of atoms has had a profound impact on many areas of atomic, molecular and optical science. In particular, ultracold atoms colliding in magneto-optical traps typically have relative kinetic energies of 300µK (~7 MHz), so free-bound absorption lines are as sharp as bound-bound lines. Moreover, because of very long range centrifugal barriers, only a few collisional partial waves are important (J^'' = 0, 1 and 2 in our work on ³⁹K). Such photoassociative free-bound absorption allows observation of ``pure long-range molecule" states (R<sub>e</sub> = 28 and 39 Å in <sup>39</sup>K<sub>2</sub>) as well as long-range levels of known short range states with outer classical turning points of ~20 - 250 Å. Such spectra have been observed by ``trap loss" (decrease in atomic fluorescence), molecular ionization, and fragment ionization. Optical-optical double resonance (OODR), e.g. through the ``Franck-Condon windows" of the ``pure long-range" states, produces readily assignable spectra at higher asymptotes as well. Further extensions of ultracold photoassociative spectroscopy and applications to determination of long range potentials, atomic properties, and Bose-Einstein condensate stability will be presented.