Time-resolved infrared diode laser spectroscopy of jet-cooled FeCO and Fe(CO)2 radicals produced by the UV photolysis of Fe(CO)5

Time-resolved infrared diode laser spectroscopy was applied to the observation of jet-cooled iron carbonyl radicals, FeCO and Fe(CO)2, produced by the ArF excimer laser photolysis of iron pentacarbonyl, Fe(CO)5. The rotational temperature of 38±6 K was observed for FeCO. Simplification of the spectrum caused by jet cooling facilitated the assignment of the ν3 band of Fe(CO)2, whose band origin was determined to be 1928.18408(13) cm−1. It was confirmed by the observation of alternatively missing spin components in the ν3 band spectrum of Fe(CO)2 that this radical is linear and symmetric (D∞h) and that the electronic ground state is of 3Σg− symmetry.