SPECTROSCOPY AND PHOTODISSOCIATION OF DIMETHYLZINC IN SOLID ARGON - 1- VACUUM UV LUMINESCENCE DETECTION SYNCHROTRON-RADIATION PHOTOLYSIS

Absorption spectra of thin-film DMZ/Ar samples, prepared by condensing gaseous mixtures of dimethylzinc (DMZ) with argon at 12 K, were recor ded in the region of the first dissociative absorptions of DMZ centere d in the gas phase at 200 nm. Large blue shifts are observed in the ma trix spectra which can be related to the Rydberg-like characteristics of these excited states of DMZ. The photochemistry of DMZ in an argon matrix was investigated either by subjecting samples to undispersed sy nchrotron irradiation using a quartz filter to select a wavelength ran ge above 155 nm or to wavelength-specific irradiation. Steady-state an d time-resolved luminescence spectroscopy of the dissociation products isolated in solid argon indicate the existence of atomic zinc strongl y perturbed by a methyl radical in freshly photolyzed samples, which y ields truly isolated atomic zinc upon annealing to 33 K. Dissociation threshold measurements indicate a barrier of 25 kcal/mol for direct ca ge escape of atomic zinc in the Ar lattice. The increased intensity of Zn(P-3(1))/Ar emission observed in photolyzed DMZ/Ar samples relative to pure Zn/Ar samples is explained in terms of the enhanced ISC of at omic zinc in the presence of hydrocarbon species in the former samples , This has been shown by codeposition of atomic zinc with Ar doped wit h CH4 and C2H6.