NEAR INFRARED LASER SPECTROSCOPY OF NiI

Abstract

Laser induced fluorescence spectrum of NiI in the near infrared region 714 - 770 nm has been recorded and analyzed. Eleven bands belonging to four electronic transition systems have been observed: the $(0,0), (1,0)$, and (2,0) bands of $[13.3] ^{2}\Sigma^{+}- A {^{2}}\Pi_{3/2}$ system; the (0,0), (1,1) and (0,1) bands of the $[13.9] ^{2}\Pi_{3/2}-X {^{2}}\Delta_{5/2}$ system; the (0,0) and (1,0) bands of $[13.9] ^{2}\Pi_{3/2} - A ^{2}\Pi_{3/2}$ system; and the (0,0), (1,1) and (0,1) bands of the $[14.0] ^{2}\Phi_{7/2} -X ^{2}\Delta_{5/2}$ system. Spectra of isotopic molecules confirmed the vibrational quantum number assignment of the observed bands. Least squares fit of observed rotational lines yielded accurate molecular constants for the $[13.3] ^{2}\Sigma^{+}, [14.0] ^{2}\Phi_{7/2}$ and the $A ^{2}\Pi_{3/2}$ electronic states of NiI. Hot band transition from the $v = 1$ level of the $X ^{2}\Delta_{5/2}$ state gives $\Delta G_{1/2} = 276.67 cm^{-1}$. The $A ^{2}\Pi_{3/2}$ state was determined to be only $163.85 cm^{-1}$ above the $X ^{2}\Delta_{5/2}$ state.