VIBRATIONAL ANALYSIS OF THE 460 NM BAND SYSTEM OF NICKEL DICHLORIDE PRODUCED IN A FREE JET EXPANSION

Using a free-jet expansion which incorporates a heated nozzle, we have recorded the laser excitation spectrum of the 460 nm band system of NiCl 2 at a rotational temperature of ∼ 40 K. 35Cl/ 37Cl isotope shifts were resolved which permit the assignment of progressions involving the symmetric stretching vibrational mode and identify a triplet splitting with spacings of 96 and 149 cm-1 which is believed to be due to spin-orbit coupling. Sequence bands involving the bending vibrational mode are also tentatively assigned. Only a small change in the symmetric stretching vibrational wave number is found between the electronic states involved in this transition (ṽ′1 = 356 cm -1, ṽ″1 = 360 cm-1 ). This result and the triplet splitting observed are discussed with respect to the possible electronic states involved and the assignment of this band system as either a Laporte forbidden g↔g transition involving the d orbitals on the Ni atom or an allowed u↔g charge transfer transition. © 1990 American Institute of Physics.