Laser spectroscopy of NiBr: new electronic states and hyperfine structure

Laser induced fluorescence spectrum of NiBr in the visible region between 604 and 666 nm has been recorded and analyzed. Fourteen bands belonging to three electronic transition systems, namely, 15.1] (2)Delta(52)-X (2)Pi(32), 15.1] (2)Pi(32)-X (2)Pi(32), and 14.0] (2)Delta(52)-X (2)Pi(32) have been observed. Spectra of isotopic molecules were also observed and analyzed. Detailed analysis of the recorded spectra indicated that the two electronic states 15.1] (2)Pi(32) and 15.1] (2)Delta(52) lie about 1 cm(-1) apart from each other and J-dependent perturbation due to spin-uncoupling interaction has been observed. Least squares fitting procedures involving deperturbation matrix elements were used to fit the observed line positions, which yielded accurate molecular constants for the 15.1] (2)Pi(32) and 15.1] (2)Delta(52) states. In addition, the (1,0) band of the 15.1] (2)Delta(52)-X (2)Pi(32) transition shows partially resolved hyperfine structure that was caused by the interaction of unpaired electron with the magnetic moment of the Br nucleus (nuclear spin of I=32) in the excited state. The rapid decrease in hyperfine width as J increases suggests that the hyperfine coupling in the excited state conforms to Hund's case (a(beta)) coupling scheme.