The hyperfine interaction in the A 2Pi1/2 and X 2Sigma+ states of ytterbium monofluoride

The fine and hyperfine interaction parameters in the A (2)Pi(1/2)(v=0) and X (2)Sigma(+)(v=0) states of the odd metal nuclear spin isotopologues of ytterbium monofluoride, (171)YbF and (173)YbF, have been determined from an analysis of high-resolution laser induced fluorescence spectra of the A (2)Pi(12)<--X (2)Sigma(+)(0,0) band. The observed ground X (2)Sigma(+)(v=0) state (171)Yb(I=1/2) Fermi contact parameter is significantly smaller than that determined from the matrix isolation electron spin resonance measurement [Van Zee et al., J. Phys. Chem. 82, 1192 (1978)]. An interpretation of the (173,171)Yb magnetic hyperfine and nuclear electric quadrupole coupling parameters is given.