No abstract

Abstract. The dependence of primary photophysical and photochemical processes, especially of electron photoejection, in phenol and related compounds in aqueous solution on excitation intensity and excitation energy is examined. Theoretical and experimental evidence is presented for the possibility of three pathways for electron ejection: (1) A monophotonic pathway via the fluorescent state, which most probably does not involve the lowest triplet state; (2) a monophotonic pathway requiring higher excitation energies, which takes place in competition with internal conversion to the fluorescent state; and (3) a consecutive biphotonic pathway in which the lowest triplet state absorbs the second photon, and which can become predominant at high intensities, e.g. under flash conditions. It is shown that this model reconciles apparently conflicting results published in the literature.

No abstract

No abstract

No abstract

Abstract--The radiation-induced decomposition of biological resistant pollutants in drinking as well as in wastewater is briefly reviewed. First, some important units, definitions etc., radiation sources, as well as dose-depth curves in water as functions of the electron energy and 6°Co-y-rays are mentioned. Following is a schematical presentation of water radiolysis and of characteristics of primary free radicals. Then the degradation of some aliphatic and aromatic chlorinated compounds in the presence of air is presented. Some spectroscopic and kinetic data of transients resulting from chlorinated phenols are also quoted in order to illustrate and to explain the rather complicated degradation mechanisms. In this respect the synergistic effect of radiation and oxygen as well as that of ozone is also discussed. Finally, a scheme for technical application of high energy elelctron beam is presented.

No abstract

The yield of the primary products of the liquid water photolysis at 1236 Å and 1470 Å is reported. It was found that besides the dissociation of the excited water molecules into H and OH radicals probably e− aq is also formed. The H and OH radicals were scavenged by means of formate, and the e− aq together with a part of H2O* by adding carbon dioxide. The quantum yields determined at 1236 Å are: Φ(H, OH) = 1.03 ± 0.02, 0.06 < Φ(e− aq, H2O*) < 0.12 and at 1470 Å: Φ(H, OH) = 0.72 ± 0.02, 0.037 < Φ(e− aq, H2O*) < 0.075. The quantum yield of high purity liquid water at 1849 Å in absence of any scavengers is Φ(H, OH) = 0.022. Previously published data by us for 1849 Å are also given: Φ(H, OH) = 0.33 ± 0.01, 0.02 < Φ(e− aq, H2O*) < 0.04. Reaction mechanisms are proposed.