Theory of coherent photoassociation of a Bose-Einstein condensate - art. no. 063616

We study coherent photoassociation, phenomena analogous to coherent optical transients in few-level systems, which may take place in photoassociation of an atomic Bose-Einstein condensate but not in a nondegenerate gas. We de velop a second-quantized Hamiltonian to describe photoassociation, and appl y the Hamiltonian both in the momentum representation and in the position r epresentation (field theory). The solution of the two-mode problem, includi ng only one mode each for the atomic and molecular condensates, displays an alogs of Rabi oscillations and rapid adiabatic passage. A classical version of the field theory for atoms and molecules is used to demonstrate that, i n the presence of photoassociating light, a joint atom-molecule condensate is unstable against the growth of density fluctuations. Experimental compli cations, including spontaneous emission and unwanted "rogue" photodissociat ion from a photoassociated molecule, are analyzed. A two-color Raman scheme is studied as a method to set up an effective two-mode scheme with reduced spontaneous-emission losses. We discuss photoassociation rates and photoas sociation Rabi frequencies for high-lying vibrational states in alkali dime rs both on the basis of molecular-structure calculations, and by comparing with an experiment [Wynar et al., Science 287, 1016 (2000)].