MOLECULAR-BEAM OPTICAL STARK SPECTROSCOPY OF YF

The molecular-beam-optical Stark spectrum of the B-1-pi(upsilon = 0) - X 1-SIGMA+ ( upsilon = 0 band system of YF has been recorded and analysed. The permanent electric dipole moment mu and the magnetic hyperfine parameter a for the B 1-PI state were exerimentally determined to be 2.96(4) D and 146.8(3) MHz and the experimentally determined value for mu(X 1-SIGMA+ ) is 1.82(8) D. The sign of the magnetic hyperfine parameter indicates that the major contribution to the B 1-PI-state is form a...pi-delta-configuration. The determined mu(X 2-SIGMA+ ) value is compared with theoretical predictions and the ratio mu(X 1-SIGMA+)/mu(B 1-PI) is rationalized in terms of plausible is molecular orbital descriptions for two electronic states.