10min:

C. LINTON, Physics Department, University of New Brunswick, P.O. Box 4400, Fredericton, New Brunswick, E3B 5A3, Canada; T. C. STEIMLE AND D. M. GOODRIDGE, Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287-1604.

Previous experimental spectroscopic data on the ytterbium monoxide molecule, YbO, has indicated that the ground state is a ¹⁺ state originating from the closed 4f¹⁴ configuration of the Yb⁺² ion. Ab initio calculations have consistently placed the low-lying states of the 4f¹³6s superconfiguration below that of the 4f¹⁴ configuration. The 4f¹³6s superconfiguration is expected to have the smaller dipole moment because of the large back-sided polarization of the 6s orbital. We therefore decided to try and measure the dipole moment in an attempt to resolve this issue and gain a better understanding of the configurational nature of the ground state. A supersonic molecular beam of ytterbium monoxide, YbO, was produced by reacting Yb atoms with oxygen in a laser ablation source, passing the beam through a pair of Stark plates and applying an electric field. The beam was interrogated by a single mode ring dye laser tuned to the R(1) line of the \Omega = 0⁺ - X¹⁺ transition at 579~nm and, from the Stark shifts of the lines, a dipole moment of ~ 5.8 Debye was determined for both states. The details of this investigation will be presented and the results discussed in terms of the electron configurations of the two states.