Observation of the FeNC molecule by laser fluorescence excitation spectroscopy

A new molecular electronic band system has been observed in the near UV by laser fluorescence excitation in a free-jet supersonic expansion of photoly zed Fe(CO)(5) diluted in seed gases containing acetonitrile. The three obse rved bands displayed the rotational structure of a Omega'=7/2 <-- Omega"=9/ 2 transition and could be assigned as an excited-state progression in a sin gle vibrational mode. The rotational constant B" and its change upon isotop ic substitution in acetonitrile [(CH3CN)-C-13] was consistent with the assi gnment of the molecular carrier as the linear FeNC molecule. In analogy wit h the iron monohalides, which have electronic band systems in the same wave length range, the transition can be described as a 4p <-- 4s excitation. Th e derived structure is compared with that of other metal-containing cyanide /isocyanide molecules. (C) 2001 American Institute of Physics.