15min:

ANTHONY J. MERER AND JAMES R. D. PEERS, 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.

Zirconium monocarbide is produced in high yield from the reaction of laser- ablated Zr metal with a helium/methane (1%) gas mixture under supersonic free jet conditions. The ground state is X^{1 +}, but the low-lying a^{3 +} state has also been identified by high-resolution laser-induced fluorescence; this has T₀ = 690~ cm^{- 1} and _e = 885~ cm^-1. Molecular constants have been derived for ⁹⁰ZrC (51.45% natural abundance) for both states; the corresponding constants of the minor isotopomers ⁹²ZrC (17.15%) and ⁹⁴ZrC (17.38%) have also been determined for a^{3 +}, and scale isotopically within experimental error. The principal electronic bands in the visible region form a strongly perturbed ³ _r - a^{3 +} system, of which the origin band has been analysed in detail. The perturbations in the ³ _r state appear to be caused by singlet states.