15min:

DENNIS J. CLOUTHIER, Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055; ANTHONY J. MERER, Department of Chemistry, University of British Columbia, Vancouver, BC, Canada V6T 1Z1; SCOTT J. RIXON, Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC, Canada V6T 1Z1; THOMAS D. VARBERG, Department of Chemistry, Macalester College, St. Paul, MN 55105.

New high resolution spectra of the B1/2 (^{2 +}) - X^{2 +} transitions of LaNH and LaND, near 16000 cm^-1, have been obtained under jet-cooled conditions, following the reaction of laser-ablated lanthanum metal with NH₃ and ND₃. Rotational analyses have given the ground state structure as r₀(La-N) = 1.932072(11) Å; r₀(N-H) = 1.01357(31) Å. Strong vibronic and spin-orbit coupling is found to occur between the B state and the ò state near 12600 cm^-1. This causes various interesting effects: the hyperfine line strengths in the B - X transition are unusual, showing that, though it is nominally ² - ² , both parallel and perpendicular transition moments are present; also the bending frequency of the B state is raised by 150 cm^-1 compared to the ground state, while its vibrational structure shows large l-dependent ``spin-vibration'' splittings which can be represented by A_sv l, where A_sv eq -14 cm^-1.