HYPERFINE-STRUCTURE IN PHOTOASSOCIATIVE SPECTRA OF LI-6(2) AND LI-7(2)

We present spectra of hyperfine resolved vibrational levels of the A(1 ) Sigma(u)(+) and 1(3) Sigma(g)(+) states of Li-6(2) and Li-7(2) obtai ned via photoassociation of colliding ultracold atoms in a magneto-opt ical trap. A simple first-order perturbation theory analysis accuratel y accounts for the frequency splittings and relative transition streng ths of all observed hyperfine features. Assignment of the hyperfine st ructure allows accurate determination of a vibrational level center of gravity, which significantly decreases the experimental uncertainty o f vibrational energies. Differences in the spectra of Li-6(2) and Li-7 (2) are attributed to quantum statistics. The 1(3) Sigma(g)(+) series obeys Hund's case b(beta S) coupling and the hyperfine constant is ext racted for both isotopes.