Spectroscopy of the CH₃Zn radical. Vibrational frequencies and electronic configurations of the X̃, Ã, and C̃ states

Abstract

The monoalkyl zinc radical, CH3Zn, may be observed by laser-induced fluorescence following UV photodissociation of (CH3)2Zn. The fluorescence spectrum obtained upon excitation of the 000 and the 210 bands of the Ã-X̃ transition was assigned. A very simple fluorescence spectrum is obtained upon excitation of the 000 band, allowing assignment of the fundamental vibrational frequencies for the CZn stretching mode (v3, 445 cm-1) and the CH3 umbrella mode (v2, 1060 cm-1) of the X̃ state. A much more complicated, time-dependent and pressure-dependent fluorescence spectrum is obtained upon excitation of the 210 band. Collisionally induced energy redistribution within the à state during its radiative lifetime populates v = 1 of v3 and the upper spin-orbit level of the à state. Observation of fluorescence from these levels allows assignment of v3 (545 cm-1) and the spin-orbit splitting (255 cm-1) of the à state. The symmetry species and electronic configurations of the X̃ and à states are assigned by comparison to the analogous states of ZnH. A similar comparison allows assignment of a set of higher energy bands observed by Young, Gosavi, Connor, Strausz and Gunning to the C̃-X̃ transition of CH3Zn. The B̃-X̃ transition has not been observed due to very poor Franck-Condon overlap between the B̃ and X̃ vibrational states. © 1990.