SPIN-ROTATION AND HYPERFINE-STRUCTURE IN THE X2-SIGMA+ STATE OF YTTRIUM MONOSULFIDE BY MOLECULAR-BEAM LASER-RADIO-FREQUENCY DOUBLE-RESONANCE

The molecular-beam laser-radio-frequency double-resonance method has been used to measure the spin-rotation and magnetic hyperfine structure of yttrium monosulfide (YS) in its X2-SIGMA-+ electronic ground state. The spin-rotation constant gamma is found to be positive, unlike that of YO. The Fermi contact and dipolar hyperfine interactions (due to the spin I = 1/2 of Y-89) are found to be rather close to the corresponding quantities in YO. The contact hfs constant b in the excited B2-GAMMA-+ state of YS was determined by combining the directly measured X2-SIGMA-+ splitting information with B-X optical hfs observations.