title: [Impulse photoconductance of solutions of chlorophyll and its analogs. IV. Absolute quantum yield of ion radical formation during photooxidation of chlorophyll a by n-benzoquinone].
abstract: The values of absolute quantum yield phi of the formation of free ion-radicals during the illumination of alkohol solutions of chlorophyll alpha (Chl) and rho-benzoquinone (Q) at room temperature were obtained by the method of impulse photoconductance. With an increase of the dielectric constant epsilon of the solvent from approximately 6 to approximately 25 phi increases by two orders ( approximately 10(-3)--approximately 10(-1). That obtained relationship phi (epsilon) is explained by epsilon effect on the efficiency of dissociation of "solvent-shared" ion-radical pair Chls+. Os-. The comparison of experimental data and theoretically expected ones allowed the estimation of some parameters to be obtained which characterize the ion-radical pair: interionic distance (10 A), the dissociation velocity constant ( approximately 10(5)--10(8) s-1), the velocity constant of reverse electron transfer (10(8) s-1), the life time approximately 10(-8) s).
mesh_terms: D002734:Chlorophyll / Q000528:radiation effects*; D004579:Electron Transport; D007477:Ions; D008027:Light; D010084:Oxidation-Reduction; D011809:Quinones; D012542:Scattering, Radiation
chemical_list: D007477:Ions; D011809:Quinones; D002734:Chlorophyll
vernacular_title: Impul'snaia fotoprovodimost' rastvorov khlorofilla i ego analogov. IV. Ob absoliutnom kvantovom vykhode obrazovaniia ion-radikalov pri fotookislenii khlorofilla a n-benzokhinonom.