Hyperfine structure in the A4Π-X4Σ - (0, 0) band of MoN

Abstract

The (0, 0) band of the A 4Π-X 4Σ - transition of MoN, between 590 and 635 nm, has been studied using the sub-Doppler technique of intermodulated laser-induced fluorescence spectroscopy. Spectra taken at a resolution of about 60 MHz showed resolved hyperfine structure, which is caused principally by the unpaired 5sσ electron in the ground state interacting with large magnetic moment of the 42 95Mo and 42 97Mo nuclei with nuclear spin I = 5/2. The hyperfine structures of the ground state vary with J in the manner expected for spin uncoupling from case (a β) to case (b βJ). This band is notable for its complex appearance due to a combination of the high-spin multiplicity transition and the presence of seven isotopic species. Least-squares fits of the observed hyperfine line positions have yielded comprehensive sets of rotational, spin, and hyperfine parameters for the A 4Π and X 4Σ - states of 95MoN and 97MoN. The hyperfine parameters are interpreted and give information about the electron distribution in the molecule. Improved molecular constants of other isotopomers with zero Mo nuclear spin are also reported.