Vibrational structure in the laser excitation spectrum of nickel dichloride at 360 nm

Abstract Nickel dichloride has been formed “cold” in the vapor phase by heating the solid to about 750°C, entraining the vapor in a high pressure of argon and expanding it supersonically through a small hole into a vacuum chamber. The laser excitation spectrum of the sample prepared in this way has been recorded in the region of 360 nm. Under these conditions, it is possible to resolve both vibrational and rotational fine structure. The same spectrum was recorded when carbon tetrachloride vapor was passed over the hot metal and expanded through the nozzle. Some “hot” bands have been identified by dispersing the fluorescence with a small monochromator. Virtually no chlorine isotope structure could be identified, even when isotopically enriched samples were used. A partial analysis of the vibrational structure has been achieved in which several progressions in the symmetric stretching vibration have been identified. These progressions are consistent with a value for v 1 of 360 cm −1 for the lower electronic state and 345 cm −1 for the upper electronic state. The complications in the observed spectrum may be caused by two or more upper electronic states being involved in the band system.