Masato Noda

Electronic Spectra of Trapped Electrons in Organic Glasses at 4°K

The optical absorption spectra of trapped electrons were observed in γ‐irradiated ethylene glycol–water, methanol, 10M NaOH, and MTHF at 4°K. The prominent infrared absorption bands were observed in ethylene glycol–water and ethanol glasses, while the bands in methanol, 10M NaOH, and MTHF glasses were similar in shape, slightly red shifted, to the bands for the radiolysis at 77°K. When the glasses were warmed to 77°K, the bands changed irreversibly into those for the radiolysis at 77°K, reducing the absorption intensity. The spectral changes at the intermediate temperatures between 4°K and 77°K were recorded for ethylene glycol–water and methanol cases. The results are interpreted by the molecular reorientation model proposed in the previous paper [T. Higashimura, M. Noda, T. Warashina, and H. Yoshida, J. Chem. Phys. 53, 1152 (1970)].

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.

Electron Traps in Irradiated Water–Ethylene Glycol Glass at 4 and 77°K

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 m...

Asymmetrical radical formation in D- and L-alanines irradiated with tritium-β-rays

Radical formation in D- and L-alanines was studied using ESR after internal3H-β-irradiation under the situation in which the contribution of Bremsstrahlung to form the radicals is assumed to be considerably less than the case of9 0Y-β-irradiation. It was demonstrated that the relative radical concentration by the β-rays was distinguishably higher in D-alanine than in L-alanine. Thus the asymmetry found in these experiments in the radical formation of the alanines may be attributed to the different interaction between the polarized electrons and the two enantiomers.

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.

An approach to the mechanism of the asymmetrical radical formation in yttrium-90-beta-irradiated D- and L-alanines.

Several attempts were made to investigate the mechanism of the asymmetrical radical formation in yttrium-90-beta-irradiated D- and L-alanines which was reported in the preceding paper (1). The experiments demonstrated that the magnitude of the asymmetry was dependent on beta-ray dose, namely the lower the dose the larger the observed difference was, and that no difference could be detected when the alanines were irradiated in aqueous state. The results in the present study seem to that different interaction between the crystal structure of the two enantiomers and polarized beta-rays may be responsible for the observed phenomenon.

Asymmetrical Radical Formation in β-Irradiated D- and L-Alanines

It was demonstrated that the relative radical concentration was distinguishably higher in D-alanine than in L-alanine when irradiation was carried out by using yttrium-90 β-ray source. On the other hand, when irradiation was carried out by using non-polarized β-rays derived from Van de Graaf generator, no such difference was observed in the radical formation of both alanines. The results suggested that some process being involved in the parity non-conservation in a β-decay must play an important role in the observed phenomenon.

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.