15min:

A. S-C. CHEUNG, H. F. PANG, W. S. TAM, J. YE AND J. W-H. LEUNG, Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong..

Two new electronic transition systems of NiI namely: the [14.0] ² _7/2 - X² _5/2¬ and the [15.7] ² _5/2¬ - X² _5/2¬ transitions were observed and analyzed using laser vaporization/reaction supersonic free jet expansion and high resolution laser induced fluorescence spectroscopy. In addition, the (v, 0) bands with v = 6 - 10 of the previously identified [14.6] ² _5/2¬¬ - X² _5/2 transition were found to be perturbed by the [15.7] ² _5/2¬¬ state. All observed spectra show partially resolved hyperfine structure. Hyperfine width of rotational lines decreases rapidly as J increases suggested that the hyperfine structure for the [14.0] ² _7/2, the [14.6] ² _5/2¬ and the [15.7] ² _5/2¬ states conform to the Hund's case a_ coupling scheme. The interaction between the [14.6] ² _5/2¬ and the [15.7] ² _5/2¬ states is evident in the progressive increase in hyperfine width in rotational lines of the [14.6] ² _5/2¬ - X² _5/2 transition as the vibrational quantum number increases. Deperturbation procedures were successfully applied to analyze the interaction between these two states. Accurate molecular and hyperfine constants for the [14.0] ² _7/2¬, the [14.6] ² _5/2¬ and the [15.7] ² _5/2¬¬ states were obtained and interpreted.