Analysis of the Electronic Spectrum of Dimethylzinc and Perdeutero-Dimethylzinc Cations

Fred J. Grieman

The electronic spectrum of the A2A1s-X2A4s transition of the Zn(CH3)2 cation observed near 608 nm has been obtained (via electron impact of a free jet expansion) and assigned previously [Grieman, Fujikawa, Phillips, J.Phys.Chem., 100, 9276 (1996)]. To further study this cation and to confirm the previous assignment, the analogous spectrum for the perdeuterated molecular ion, Zn(CD3)2+, has been observed near 602 nm and the main features completely assigned. The observed isotopic shifts of the vibronic features, when compared to a calculation of vibrational mode energies for these cations, do confirm previous assignments of the CH3 symmetric deformation vibrational mode.  Further analysis of the perdeutero- spectrum revealed a band which is assigned to the C-Zn-C symmetric stretching vibrational mode, resulting in the identification of the corresponding (weak) band in the perhydro- spectrum.  Combination bands discovered in both spectra confirm these assignments.  Whereas the CH3 symmetric stretching vibrational energy was found to decrease only slightly upon ionization of the Zn(CH3)2 molecule, the C-Zn-C symmetric stretching vibrational energy was found to decrease significantly.

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