Further observations of the 460 nm band system of nickel dichloride, cooled to lower temperatures in a free jet expansion

The 460 nm band system of NiCl2, formed in a free jet expansion, has been recorded under colder conditions than achieved previously by a simple modification of the heated nozzle source. The spectrum is considerably simplified, permitting several weak, new features to be observed. In particular, bands which involve the excitation of two additional quanta of the bending vibration ?2 in the upper state are observed, yielding values for Image '2 and Image ?2 of 61.1 and 87.1 cm-1, respectively. The origin of the fine-structure splitting and the ordering of the spin components is also determinable from this spectrum. Weak features which may be sequence bands in the antisymmetric stretching vibration ?3 have also been observed.