Akira Namiki

Trapped Electrons Produced in Ethanol Glass at 4°K

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.

Electronic Spectra ot trapped electrons in organic glasses at 4°K: VI. Photobleaching ethanol

Abstract The absorption spectrum of e t - in ethanol is composed of three bands, suggesting the existence of various kinds of traps. The retrapping phenomenon and the increase of the Bz radical were observed after photobleaching e t - at 4°K, but not e s - . The photo-transition of e t - is a bound-free one, but that of e s - may be a bound-bound one.

Ionic intermediates produced by gamma irradiation at 4 K: Halogenated naphthalene and benzene derivatives in ethanol

Optical absorption and ESR measurements have been performed for the irradiated halogenated benzene and naphthalene derivatives in ethanol at 4 K. The anions of both bromo− and chloronaphthalene derivatives were observed under steady state at 4 K, while the former anion at 77 K results in dissociation and the latter anion results in protonation. Both anions of benzene and fluorobenzene were stable at 4 K, whereas not at 77 K, indicating that protonation is inhibited at 4 K. Irradiated iodobenzene and bromobenzene solutions at 4 K showed a doublet band whose energy separation was 0.8−0.9 and 0.41−0.48 eV, which are close to the energy separation between 2P3/2 and 2P1/2 of I and Br, respectively. The transition energies of the long wavelength bands of these compounds and of chlorobenzene is linear with the ionization potentials of respective halide ions with a slope of close to unity. Therefore these bands may be assigned to an electron transfer band from halide ion to its counterpart benzene ring. As the el...

Absorption spectra of anions of aromatic ketones in ethanol glasses at 4.2°K

Abstract Anions of benzophenone, acetophenone, and 4-hydroxy-benzophenone were produced in ethanol at 4.2°K by steady γ irradiation. Their absorption spectra are significantly different from those obtained in ethanol at 77°K, but change into the same spectra on raising the temperature. The spectra at 4.2°K are due to the pre-solvated anions of these compounds.

Electron scavenging in ethanol glasses containing two scavengers

Abstract Ethanol glasses with equimolar concentrations of biphenyl and benzychloride are irradiated with γ-rays at 77 and 4.2 K. The yield of biphenyl anion increases, reaching a maximum and decreases with increasing concentration of the scavengers. The concentration at the maximum depends on the temperature of irradiation. These phenomena were interpreted by the tunneling of the electron from the trapped state to the neutral biphenyl and that from the biphenyl anion to the neutral benzychloride.