15min:

ZYGMUNT J. JAKUBEK AND BENOIT SIMARD, Steacie Institute for Molecular Sciences, National Research Council, Ottawa, ON, Canada K1A 0R6; WALTER J. BALFOUR, Department of Chemistry, University of Victoria, Victoria, BC, Canada V8W 3V6.

Stark spectra for four bands of yttrium hydride in the 19300-19800 cm^-1 region have been recorded by exciting the molecules in the presence of external electric field up to 16 kV/cm and monitoring laser induced fluorescence. The molecules have been produced in a free jet molecular beam apparatus by laser vaporizing yttrium metal in the presence of He carrier gas doped with 2-5% of H₂ or NH₃. Rotational and quantum number assignments of the bands have been established with the help of Stark effect. The electric dipole moments have been measured to be equal to: 1.569(64), 2.325(8), 3.316(11), 2.273(6), and 1.537(8) for the X^{1 +} ground state and the 19385, 19746, 19572, and 19575 cm^-1 excited states, respectively. Strong variation of the effective quantum number with J has been detected for the lowest rotational levels of the 19572 cm^-1 state. The effective values have been determined to be equal to =1 (fixed value), =1.472(7), and =1.624(18) for J=1, J=2, and J=3, respectively. Possible perturbers of the 19572 cm^-1 state will be considered. Electronic character of the ground state and the four excited states will be discussed. Correlation of the dipole moment and the quantum number in Stark spectroscopic measurements will be analyzed and required experimental conditions for breaking of such correlation will be determined.