Reactions of photogenerated fluorine atoms with dopant molecules in solid argon .1. Photolysis of solid Ar-CH4(CD4)-F-2 mixtures at 13-16 K

The products of UV photolysis of ternary Ar-CH4(CD4)-F-2 mixtures (1:c:c(0), c, c(0) = 0.001-0.01) at 13-16 K were identified by ESR and FTIR spectroscopy. These products are (CH3)-C-.((CD3)-C-.) radicals of types I and II and molecular CH3F-HF complexes. The latter were characterized by the IR bands of the stretching C-F (1003 cm(-1)) and H-F (3774 cm(-1)) vibrations. The ESR spectra of radicals I are asymmetric. The anisotropy of the g-factor (Delta g approximate to 10(-3)) of radical I indicates that the structure of the radicals is nonplanar. The ESR spectrum of the type II radical is identical to that of matrix-isolated (CH3)-C-.((CD3)-C-.) radicals with the planar structure (Delta g < 5.10(-5)). Under the experimental conditions, the amount of complexes formed in the photolysis is equal to 0.022.c. When the photolysis is ceased, radical I disappears after similar to 10(3) s and radical II is stabilized. The limiting concentrations of the stabilized (CH3)-C-. and (CD3)-C-. radicals are equal to 2.10(-2).c and 2.10(-3).c, respectively. A mechanism of the formation of the products is suggested. It is based on the assumption that both matrix-isolated CH4 and F-2 and their heterodimers CH4-F-2 are present in the samples and it takes into account the long-range migration of translationally excited flourine atoms. The CH3F-HF complexes and radicals I are generated by the photolysis of the CH4-F-2 heterodimers. The decay of radicals I is caused by geminate recombination of proximate F...CH3 pairs. Radicals II are formed in the reaction of translationally excited fluorine atoms with isolated CH4 (CD4) molecules.