The title compounds, acyclic phenyl nitrones with functional groups, cyclic dinitrones with conjugated or isolated double bonds, and imidazoline nitrones are studied as spin traps (ST) for short-lived free radicals (R) generated photochemically in solution and in the gas phase. New STs are efficient in trapping OH, hydroxyalkyl, or HO2 radicals. EPR spectra of the spin adducts (SA) of studied dinitrones are triplets of doublets characteristic of the nitroxides with one radical center. Imidazoline ST with amino nitrogen exhibits pH-dependent hyperfine splittings of its SAs. Some spin traps were shown to be efficient in detecting R in the atmospheric experiments.

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This paper deals with the study of the kinetics of photolysis and photonucleation of acetaldehyde (AA) vapor in air and in nitrogen along with physical and chemical characteristics of the formed aerosol particles. Free radicals accompanying photonucleation were identified using the electron spin resonance spin-trapping technique. Numerical modeling of the photonucleation kinetics of AA, based on experimental results, was carried out. Rate of generation of primary products, leading to the nanoparticles, and the aerosol yield were evaluated. Chemical mechanism of stages leading to photonucleation in this system was proposed.

The spectrum of the intermediate product ascribed to nitrosopentane has been detected in the photolysis of the SO*-pentane (RH)-NO mixture. This result has been interpreted in terms of the radical mechanism by assuming the H-atom abstraction from RH by the excited SO2 molecules to be the primary act. The contribution of the singlet and triplet SO2 states to the product formation rate and the ratio of the singlet-to-triplet rate constants have been evaluated. At NO pressures above 5 tom, the product formation rate significantly deviates from the Stern-Volmer dependence.

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