The hyperfine structure in the electronic A E-2 '<- X E-2 ' system of the pseudorotating lithium trimer

Sub-Doppler laser spectroscopy of the A E-2(')<--X E-2(') band of Li-3 show s well-resolved and characteristic hyperfine structures of rovibronic trans itions which can be explained in all detail by the interplay between the un derlying Fermi-contact interaction, the symmetry species of the rovibronic states and the Coriolis coupling of rotational and pseudorotational motions . Ab initio calculated electron spin densities reproduce the observed line splittings to within 3%. In this Jahn-Teller distorted molecule magnetic eq uivalence of identical nuclei is strictly valid only for rovibronic states of A symmetry. However, it also holds for rovibronic states of E symmetry i f they are of pure A vibronic origin, and it is enforced for many E states of pure E vibronic origin by Coriolis coupling. In contrast, those transiti ons which involve states with dominant K-c=0 rotation functions and/or with strong vibronic E/A mixing show significant changes in the hyperfine patte rns due to magnetic inequivalence, sometimes called "hyperfine doubling." ( C) 2001 American Institute of Physics.