Cavity Ring Down Laser Absorption Spectroscopy of NiI

The absorption spectrum of NiI between 445 and 510 nm has been investigated using the technique of laser vaporization/reaction with free jet expansion and cavity ring down laser absorption spectroscopy. Two new transitions namely, 21.3²?_5/2～X²?_5/2 and 21.9²Π_3/2～X²?_5/2 systems were identified and studied. Spectra of both ⁵⁸NiI and ⁶⁰NiI isotopic molecules were observed. Equilibrium molecular constants for both electronic states are reported and the equilibrium bond length for the 21.3²?_5/2 state and the 21.9²Π_3/2 state was respectively determined to be 2.431 and 2.481 ?.