The ultracold frontier has progressed rapidly for gaseous atoms, e.g. with achieve-ment of Bose-Einstein condensation for a number of bosonic atoms and of a degenerate Fermi gas for 40K, typically at temperatures on a nanoKelvin scale.[1]

There are now important efforts underway in many laboratories toward achieving comparable results for gaseous molecules.[2]  As first steps, alkali metal diatomic molecules (K2, Rb2 and Cs2) have been formed (up to 106/sec.) at microKelvin translational temperatures by photoassociative spectroscopy of ultracold atoms.[3]  In addition, hotter milliKelvin molecules have been formed, e.g. by helium buffer gas cooling, by atomic recombination on helium clusters, and by deceleration of dipolar molecules.  Also, several varieties of the translationally cooled molecules have been trapped.  Recent results and near term prospects for advances in ultra-cold molecules will be summarized.

Support received from the National Science foundation is gratefully acknowledged.

References:

[1] J. Weiner et al., Rev. Mod. Phys. 71, 1 (1999).
[2] J. T. Bahns, P. L. Gould and W. C. Stwalley, Advan. At. Mol. Opt. Phys. 42, 171 (1999).
[3] W. C. Stwalley and H., Wang, J. Mol. Spectrosc. 195, 194 (1999).