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) obtained via photoassociation of colliding ultracold atoms in a magneto-optical trap. A simple first-order perturbation theory analysis accurately accounts for the frequency splittings and relative transition strengths of all observed hyperfine features. Assignment of the hyperfine structure allows accurate determination of a vibrational level center of gravity, which significantly decreases the experimental uncertainty of 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 extracted for both isotopes.