Robert W. Quandt

The CO product of the reaction of O(3P) with CH3 radicals

The reaction of O(3P) atoms with CH3 radicals is shown to produce CO (in addition to the major product CH2O) which is detected by laser induced fluorescence. The rotational and vibrational temperatures of the CO product are about 2000 K. The results are explained by the assumption that the reaction takes place mainly by an indirect mechanism in which a methoxyl radical is formed and then dissociates unimolecularly.

Kinetic energies of hydrogen atoms photodissociated from alkyl radicals

Abstract A series of alkyl halides was photodissociated at 205.1 nm, forming halogen atoms and alkyl radicals. The latter were in turn dissociated at the same wavelength into alkenes and hydrogen atoms. The average kinetic energies of the hydrogen atoms are large (1.5–2.0 eV) and decrease only slowly with increasing chain length. The inference is that the dissociation mechanism involves crossing from the Rydberg state surface to a repulsive region of the ground state surface at a point near the center of a C–C bond. As had been previously found by Koplitz and coworkers, isotope scrambling was seen in CH 3 CD 2 radicals.

Translational energy release in the reaction O(3P) + H2S → H + HSO

Abstract O( 3 P) atoms were generated by photodissociating NO 2 at 351 and 308 nm in the presence of H 2 S. The average kinetic energy of the H and HSO reaction products is 9.4 ± 0.6 and 12.0 ± 0.7 kcal/mol respectively. These values are consistent with a value for the heat of formation at 0 K of HSO of − 1 kcal/mol only if the HSO product is internally cold. The elongated SO bond in the theoretical transition state and the reaction barrier imply that at least some energy will be left in the HSO radical. If the HSO product had an average of 3–4 kcal/mol of internal energy, the ab initio theoretical value for Δ f H o °(HSO) near −5 kcal/mol would be confirmed.