AMANDA J. ROSS, RAPHAEL VALLON, PATRICK CROZET AND CYRIL RICHARD, Université Lyon 1; CNRS; LASIM UMR 5579, 43 Bd du 11 novembre 1918, F-69622 Villeurbanne, France.
Fourier transform resolved laser induced fluorescence spectra have allowed us to investigate the low-lying electronic states of NiH arising from the Ni(3d9 4s1) configuration. Although laser excitation with a single mode laser should promote the molecule (formed in a hollow cathode discharge running at 1 torr pressure, with 10% H2 in argon) to a unique excited state that should be readily identifiable from the work of Kadavathu and co-workers, the resolved fluorescence spectra are unexpectedly complex. Efficient energy transfer occurs between excited electronic states, retaining only isotopic selectivity. Analysis of the spectra locates energy levels up to 8000 cm-1 above v=0 in the electronic ground state (X 2 5/2), from all components of the 2 , 2 and 2 states forming the supermultiplet complex studied by Gray et al. Measurements have been made so far for 58NiH and 60NiH. To observe heavier isotopes of nickel, an intracavity fluorescence experiment is required. Signals are increased by a factor ~25, but the signal/noise ratio in Fourier spectra is disappointing when compared with intracavity excitation results. Nevertheless, this work has allowed us almost to double the range of known energy levels below 10000 cm-1 for NiH.