Effect of polymer additives on magnetic modulation of the yield of products of recombination of triplet radical ion pairs in electron phototransfer between N,N-Dimethylaniline and pyrene. 2. Poly-N-tert-butylacrylamide in methanol

The effect of a magnetic field on the intensity of delayed fluorescence of pyrene excimers formed during evolution of pyrene — N,N-dimethylaniline radical ion pairs (RIP) in methanol containing glycerol or poly-N-tert-butylacrylamide was comparatively investigated by laser strobe fluorometry. Different methods of restricting the molecular mobility of the reagents cause different values of the magnetic effect with the same microviscosity measured with the spin probe orientational correlation time. This result contradicts the data obtained previously for mixtures with polyacrylamide and can be explained with the data on cross-linking of the polymer-containing solution. The viscosity of the microenvironment of the RIP partners is 10 times higher than the viscosity of the solvent. The presence of a maximum on the curve of the change in the magnetic effect in restriction of the molecular mobility was attributed to an increase in the lifetime of the radical pair and a change in the ratio of the relaxation rates and yield of radicals in bulk.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117334 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2059–2065, September, 1992.     

<Emphasis Type="Italic">K</Emphasis><Subscript><Emphasis Type="Italic">e</Emphasis>3</Subscript> Decay Studies in the OKA Experiment

Recent results from OKA setup concerning form factor studies in K_e3 decay are presented. About 5.25 M events obtained for decays of 17.7 GeV/cK⁺ are selected for the analysis. The linear and quadratic slopes for the decay form factor f₊(t) are measured: λ'₊ = 2.95 ± 0.022 ± 0.018 × 10 ^-2 for the linear slope fit and λ₊ = 2.611 ± 0.035 ± 0.028 × 10 ^-2, λ"₊ = 1.91 ± 0.19 ± 0.14 × 10 ^-3 for the quadratic one. The scalar and tensor contributions are compatible with zero. Several alternative parametrizations are tried: the Pole fit parameter is found to be M _V = 891 ± 3 MeV; the parameter of the dispersive parametrization is measured to be Λ₊ = 2.458 ± 0.018 × 10^-2.     

Effect of an external heavy atom on the EPR spectrum of the fluorescein semiquinone radical

The effect of an external heavy atom on the EPR spectra of radicals in homogeneous liquid solutions was investigated. Broadening of the lines in the EPR spectrum of the fluorescein semiquinone radical in water-ethanol solution was found under the effect of the external heavy atom. It was hypothesized that this broadening is due to an increase in the anisotropy of the g-factor due to potentiation of the spinorbital interaction on contact with the external heavy atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1778–1781, August, 1989.We would like to thank V. A. Roginskii for his assistance in the research and valuable advice, and B. F. Minaev for his useful discussion of the mechanism.