Hyperfine structure in photoassociative spectra of 6Li2 and 7Li2

We present spectra of hyperfine resolved vibrational levels of the A1Σu+and 1 3Σg+ states of 6Li2 and 7Li2 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 6Li2 and 7Li2 are attributed to quantum statistics. The 1 3Σg+ series obeys Hund’s case bβS coupling and the hyperfine constant is extracted for both isotopes