International Workshop on Atomic Interactions in Laser Fields - Abstracts

Photoassociation Spectroscopy: Past, Present, and Future

Paul S. Julienne

Physics Laboratory, National Institute of Standards and Technology, 100 Bureau Drive Stop 8423, Gaithersburg, MD 20899-8423 USA

 

Photoassociation spectroscopy of cold, trapped atoms has proven to be a very powerful tool for probing ground and excited state collision dynamics and interatomic interaction parameters. This talk will review the basic concepts of photoassociation, examine current work and issues, and look into future prospects.

The basic ideas of photoassociation are laid out in the original proposal by Thorsheim [1]: narrow line shapes in the laser excitation spectrum of colliding cold atoms, possibly influenced by threshold shape resonances; oscillations in the spectrum due to the free-bound Franck-Condon factors; and molecule formation due to the re-emitted light from the excited state. All of these effects have been observed and studied.

Current calculations techniques make it possible to calculate with good accuracy both the detailed line positions and intensities of photoassociation spectra, with generally good agreement between experiment and theory. Simple models are very useful for interpretation, and are often quantitative. A reflection-principle model [2,3], based on the classical Franck-Condon principle, is especially useful for providing a simple model of the line shape and light-induced level shifts that occur as the intensity of the photoassociation laser increases. Having an accurate understanding of the line shape is critical to making full use of the opportunities provided by photoassociation spectroscopy to obtain ground state scattering lengths for Bose-Einstein condensate studies.

Photoassociation is also possible in a Bose-Einstein condensate or an optical lattice site occupied by two atoms. Two color photoassociation can guide the production of molecules in specific target levels. The Raman resonance line shape can be very narrow, and lead to efficient production of cold molecules [4]. This leads to the prospects for molecular condensates.

Thanks are expressed to the Office of Naval Research and the Army Research Office for partial support.

References

  1. H.R. Thorsheim, J. Weiner, and P.S. Julienne, Phys. Rev. Lett. 58, 2420 (1987).
  2. P.S. Julienne, J. Res. Nat. Inst. Stand. Technol. 101, 487 (1996).
  3. J. Bohn and P.S. Julienne, Phys. Rev. A 60, 414 (1999).
  4. P.S. Julienne, K. Burnett, Y.B. Band, and W.C. Stwalley, Phys. Rev. A 58, R797 (1998).