High Resolution Electronic Spectroscopy of ZnCH3 and CdCH3

The number of organometallic free radicals studied spectroscopically in the gas phase has been very limited until quite recently. Application of Broida oven, laser photolysis and laser photolysis/vaporization techniques to synthesize these transient species has significantly enlarged the number of reports over the past few years. This research group’s contribution to the area have been a series of reports by Robles, Ellis and Miller detailing electronic and vibrational structures (~.5 cm-1 resolution) of 15 species of the form M-R (M = Mg, Ca, Zn and Cd; R = cyclopentadienyl (Cp), pyrollyl (Py) and methylcyclopentadienyl (MCp)) and M-CH3 (M = Ca, Zn and Cd), many of them observed for the first time.1-8 These molecules are more than simply novel constructs. The methyl and Cp derivatives are recognized as important intermediates in metal deposition processes while the metal-Py species are found as subunits in several chemical substances of biological importance. Metal-ligand bonding sites, vibrational frequencies, spin-orbit splittings and barriers to internal rotation are some of the types of information that this work has yielded. To augment this work, a rotationally resolved study is presented here which confirms the electronic state symmetry assignments given in earlier studies, and more importantly, determines rotational constants and other interaction parameters of these radicals.