First Spectroscopic Observation of the CdC2H5 Radical

We report the first spectroscopic observation of the monoethyl cadmium free radical, CdC2H5, using laser-induced fluorescence spectroscopy. This molecule was prepared in a supersonic jet by reaction of cadmium atoms with an ethyl precursor in a recently developed dual-channel electrical discharge nozzle. The laser excitation spectrum of CdC2H5 consists of a single, unresolved, band attributed to the A-X origin transition. However, the dispersed fluorescence spectrum obtained by laser-pumping the origin transition does show some vibrational structure. A short progression in the Cd-C stretching mode has been observed giving a frequency of 280 cm-1 for this mode. Comparison with the related molecule ZnC2H5 shows that the increase in reduced mass is not sufficient to account for the much lower metal-carbon stretching frequency in CdC2H5 and the evidence therefore points to a substantially weaker metal-carbon bond in the latter. The absence of vibrational structure in the excitation spectrum of CdC2H5 is attributed to the depopulation of excited vibronic levels by predissociation. Copyright 1997 Academic Press. Copyright 1997Academic Press