The role of hyperfine structure in ultracold atomic collision dynamics

Recent experiments at NIST and the University of Maryland on cooled and trapped Na atoms have revealed several 1- and 2-color spectral features associated with the hyperfine structure of the Na atom. We have calculated the adiabatic molecular potential curves in a total angular momentum basis, including hyperfine structure, of the molecular states of the alkali dimer molecules that correlate to the 2P3/2+2S separated atoms. We have also calculated the hyperfine line strengths for optical coupling to the 2S +2S ground molecular states. These are used to interpret the new experimental features for trapped Na as due to free-bound-bound or free-bound-free spectra of the Na2 molecule. New dynamical features illustrating optical control of ultracold reactions will be discussed. Supported in part by ONR