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Optical absorption and ESR measurements were carried out on et− produced in ethanol at 4°K. The same et− yield for γ radiolysis at 4 and 77°K indicates that electrons are stabilized in pre-existing traps at 4°K where molecular dipoles remain unrelaxed. et− prior to solvation can be classified into two groups. One with λmax = 1500 nm, W1/2= 4 × 103 cm−1 and Δ Hpp = 5.5 ± 0.5 G is easily photobleached by the infrared light. The other with broad absorption band in the visible and Δ Hpp = 13.5 ± 1.5 G is not photobleached by the infrared light. The successive shift of the absorption spectrum to the higher energy side on warming is interpreted by the molecular reorientation mechanism. et− decay is observed during the solvation process, depending on time required for the solvation. The blue shift of the absorption spectrum on reducing the temperature is attributed to contraction of electron traps.

In order to study the mechanism of electron trapping in irradiated glasses of water–ethylene glycol mixture, they were subjected to γ rays and examined by optical absorption and electron spin resonance measurements at 4 and 77°K. Most trapped electrons formed at 4°K give an optical absorption band in infrared region around 1800 nm and a single-line electron spin resonance spectrum with the width of 3 G, while the trapped electrons formed at 77°K give an absorption band in visible region (λmax = 585 nm) and an electron spin resonance spectrum with the width of 15 G. By warming the glass to 77°K after the irradiation at 4°K, the trapped electrons transformed to those observed for the irradiation at 77°K. Results indicate that the nature of trapped electrons formed at 4°K is very similar to that of trapped electrons in irradiated nonpolar alkane glasses. Even in the polar glass of water–ethylene glycol, the orientation of molecular dipoles is not needed for the formation of electron traps at 4°K, where the molecular movements are highly restricted. By raising the temperature to 77°K, the molecular dipoles in the vicinity of trapped electrons orient favorably to deepen the traps. The yield of trapped electrons, for 100 eV energy absorbed, at 4°K is estimated to be larger than 0.6. However, it is possibly less than 2.0, the yield for the irradiation at 77°K.

By observing electron spin resonance spectra during photolysis at room temperature, kinetic behaviors of short-lived free radicals are studied in photoreduction of benzophenone in alcohols, especially in ethanol, with and without sodium methoxide. In neutral solution, diphenylhydroxymethyl radicals and hydroxyethyl radicals are observed simultaneously. This is a firm evidence, obtained from ESR, of hydrogen abstraction of excited benzophenone from ethanol. Results indicate that (1) free radicals are the most efficiently generated by the light of ∼350 nm, (2) hydroxyethyl radicals transform into diphenylhydroxymethyl radicals if the concentration of benzophenone is high, and (3) the latter radicals disappear following the second order reaction. In the presence of sodium methoxide, diphenylhydroxymethyl radicals transform into benzophenone ketyl anions. Rate constants are determined, being 3×107 and ∼104 mole−1·1·sec−1 for the combination reaction between diphenylhydroxymethyl radicals and the proton transfer reaction from diphenylhydroxymethyl radical to methoxide ion, respectively.

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