title: Laser spectroscopy of NiI: new electronic states and hyperfine structure.
abstract: Two new electronic transition systems, namely, the [14.0](2)Phi(7/2)-Chi (2)Delta(5/2) and the [15.7](2)Phi(5/2)-Chi (2)Delta(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 [14.6](2)Delta(5/2)-Chi (2)Delta(5/2) transition were found to be perturbed by the [15.7](2)Phi(5/2) state. The interaction between the [14.6](2)Delta(5/2) and the [15.7](2)Phi(5/2) states is evident in the progressive increase in hyperfine width of rotational lines of the [14.6](2)Delta(5/2)-X (2)Delta(5/2) transition as the vibrational quantum number increases. Deperturbation procedures were successfully applied to analyze the interaction between these two states. All observed spectra show partially resolved hyperfine structure, and the hyperfine width decreases rapidly as J increases suggested that the hyperfine structure conforms to the Hund's case a(beta) coupling scheme. Accurate molecular and hyperfine constants for the [14.0](2)Phi(7/2), the [14.6](2)Delta(5/2) and the [15.7](2)Phi(5/2) states were obtained and analyzed.
authors.affiliation: Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong. hrsccsc@hku.hk
authors.forename: A S-C
authors.initials: AS
authors.lastname: Cheung
authors.forename: H F
authors.initials: HF
authors.lastname: Pang
authors.forename: W S
authors.initials: WS
authors.lastname: Tam
authors.forename: J W-H
authors.initials: JW
authors.lastname: Leung