VIBRONIC SFECTROSCOPY OF $MgCH_{3} \bar{A}^{2}E \leftarrow \bar{X}^{2}A_{1}$ TRANSITION

$^{g}$R. Rubino, J. Williamson, and T. A. Miller, J. Chem. Phys. 103 (14 (1995)Author Institution: Laser Spectroscopy Facility, Department of Chemistry, The Ohio State UniversityWe report the laser excitation and dispensed fluorescence spectra of the $MgCH_{3} \tilde{A} ^{2} E \leftarrow \tilde{X} ^{2} A_{1}$ transition. Improvements to the experiment have allowed the observation of important vibronic features not previously observed. The radical was produced in a free jet expansion from the simultaneous photolysis of $Hg(CH_{3})_{2}$ and the laser vaporization of solid Mg. The use of $Hg(CH_{3})_{2}$ as a precursor substancially improves production of the radical. A $0.1 cm^{-1}$ resolution laser was used to obtain the partially rotationally resolved LIF spectra of the $6^{1}_{0}$, and $2^{1}_{0}$ transitions. Analysis of these spectra, along with the previously $reported^{g}\ 0_{0}^{0}$ band yield structural parameters which provide information about the radical’s $\bar{A} ^{2} E$ state. Besides the usual rotational constants, we have obtained information about the Jahn-Teller effect, which is dynamic and relatively weak. We have also obtained the values of the Coriolis coupling and the spin-orbit coupling constants. The fluorescence lifetime was found to be 60(7) ns for the vibrationless level of the $\bar{A}$ state and less than 15 ns for transitions involving vibrational excitation. The dispersed fluorescence spectra of the jet-cooled $MgCH_{3}$ was analyzed, and all observed $^{2} A_{1}$ state vibrational features were assigned