Hyperfine structure in photoassociative spectra of Li26 and Li2
We present spectra of hyperfine resolved vibrational levels of the A1Σ+uand 13Σ+g states of Li26 and Li27 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 Li26 and Li27 are attributed to quantum statistics. The 13Σ+g series obeys Hund’s case bβS coupling and the hyperfine constant is extracted for both isotopes.