Zen-ichiro Kuri

ESR and Optical Studies of Acyl Radicals Produced from Acyl Chlorides by Dissociative Electron Attachment in γ‐Irradiated Organic Glasses at 77°K

Dissociative electron attachment by acyl chlorides in γ‐irradiated organic glasses at 77°K has been investigated by ESR and optical absorption measurements. The MTHF and 3MP glasses containing acyl chlorides (CH3COCl, C2H5COCl, C6H5CH2COCl, C6H5COCl, C6H5CH=CHCOCl) display a similar ESR singlet. 3‐Methylpentane glass containing CH3COCl exhibits an ESR singlet or triplet depending upon solute concentration. γ‐irradiated MTHF glasses containing these solutes give the optical absorption spectra having the characteristic absorption bands in the visible and uv region. These ESR and optical absorption spectra have been assigned to acyl radicals. Illumination of γ‐irradiated samples with visible light yields alkyl radicals from CH3CO· and C2H5CO·, benzyl radicals from C6H5CH2CO·, and brings about no change in C6H5CO· and C6H5CH=CHCO·. The decay of alkyl radicals formed in 3MP has been measured at 77°K.

Effects of Gases on Irradiated Polyvinyl Chloride as Studied by Electron Spin Resonance

The radicals produced by gamma irradiation of polyvinyl chloride powder in various gases and in vacuum are observed by electron spin resonance. Different patterns are observed for the irradiation in vacuum, air, and sulfur dioxide. No electron spin resonance absorption is obtained by the irradiation in nitrogen oxide, halogens, and hydrogen sulfide. The recombination reaction velocity of the radical produced in vacuum is measured at different temperatures to get the activation energy 38 kcal/mole.

Electron Spin Resonance Studies of Gamma‐Irradiated Single Crystals of Sucrose

The electron spin resonance of gamma‐irradiated single crystals of sucrose has been measured at 9400 Mc/sec for various orientations in the magnetic field. The variations of the resonance with angle were greatest for rotation of the crystal about its b axis, which was kept perpendicular to the magnetic field. The anisotropic hyperfine structure was observed to vanish when the magnetic field is applied perpendicular to the (b, c) plane. It was ascertained that the radical formed is the type X—CH–Y, which had been proposed by Williams et al. from the data obtained from the polycrystalline samples.

Effect of Matrix on the Formation of Solvent Radicals in the Radiolysis of Alkanes in the Solid State at 77 K

The effect of the matrix on the radiolysis of 2,3-dimethylbutane, neopentane. 2,2-dimethylbutane, and isobutane in the solid state has been studied at 77 K by means of ESR spectroscopy. Though only the ·CH2CH-(CH3)CH(CH3)2 radical is formed by the γ-irradiation of 2,3-dimethylbutane in the I crystal, the CH3\overset·C(CH3)-CH(CH3)2 radical is formed by the γ-irradiation of 2,3-dimethylbutane in the II crystal. Though the t-C4H9 and neo-C5H11 radicals are formed by the γ-irradiation of pure neopentane, the formation of radicals is affected appreciably by the addition of a small amount of alkanes. When neopentane containing ethane, etc. is γ-irradiated, the solute radical is mainly formed by energy transfer form the γ-irradiated neopentane to the solute. Most of the solutes have a spherical molecular structure like that of neopentane or are smaller than neopentane. When neopentane containing 3-methylpentane, etc. is γ-irradiated, only the neopentyl radical is formed. The molecular structures of the solutes ...

Electron‐Spin‐Resonance Studies of DPPH Solutions

The effects of impurities on the ESR of DPPH in various solutions were studied. The broad quintet spectrum usually obtained with DPPH solutions becomes well resolved after dissolved gases are removed. Addition of tertiary hydroperoxides to DPPH solutions gives a triplet spectrum, which further splits into 17 lines after subsequent degassing in the case of t‐butyl hydroperoxide. From an analysis of this spectrum, a determination was made of the spin‐density distribution of the unpaired electron in a species electronically analogous to biphenylaminium ion.An aerated DPPH solution of xylene loses its paramagnetic nature in time, but regeneration of the quintet ESR spectrum of DPPH is observed if this solution is mixed with the so‐called lophine‐x compound solution kept in the dark, and then irradiated by sunlight. The interpretation of this phenomenon is that the lophine‐x compound, when irradiated by sunlight, has an odd electron which shifts onto the nonparamagnetic DPPH—O2 reaction product regenerating DP...

Behavior Of The Free Radicals Trapped In Gamma-Irradiated Compounds Which Contain Hydrogen Bonds

A series of experiments was performed which suggest that the nonreactivity of gaseous scavengers with free radicals in certain irradiated compounds is not due to inherent free radical stability but to a network of intermolecular hydrogen bonds which prevents penetration by gases. These experiments, performed on polyvinyl alcohol, cellulose, starch, arabinose, ribose, xylose, glucose, fructose, sorbose, galactose, sucrose, cellobiose, lactose, inulin, and glutamic acid demonstrated that free radicals in these compounds, although inert to gaseous scavengers, decay rapidly near the melting point or in the presence of water and react with monomers in presence of water. (D.L.C.)

Formation of excited singlet toluene in the radiolysis of alkane containing toluene in the solid phase at 77 K

Abstract When alkane containing a small amount of toluene is irradiated by γ-ray or X-ray in the solid state at 77 K, luminescence from excited toluene is observed. The formation of the excited toluene is not due to direct excitation of toluene by γ-ray or Cerenkov light, but to the rapid energy transfer from the irradiated alkane to toluene. The intensity of luminescence from the excited toluene in the cyclopentane matrix does not correspond at all to the amounts of toluene ions, which are formed by pre-irradiation. The energy transfer is not caused by a free hole and an electron, but by an exciton. Furthermore, the effect of additives on the fluorescence suggests that the Wannier exciton or mobile ion-pair is responsible for the energy transfer in cyclopentane containing toluene in the solid phase at 77 K.

Yields of excited singlet state in the radiolysis of alkane containing toluene in the solid phase at 77 K

Abstract When alkane containing a small amount of toluene is γ-irradiated in the solid phase at 77 K, excited toluene is formed by energy transfer from irradiated alkane to toluene. Fluorescence from excited singlet toluene has been measured during γ-irradiation and after nanosecond pulse irradiation. Yields of the excited singlet toluene (S) have been determined for the first time in the solid phase at 77 K and the following G -values were measured: G (S) = 0·8−0·9, 0·7, and 0·7 in the radiolysis of cyclohexane, 2,3-dimethylutane and 3-methylpentane containing toluene (0·2 mol dm −3 ), respectively. The rate constants for energy migration, obtained experimentally from the kinetics, are of the same order of magnitude as those calculated by the theory of exciton migration.

Electron Spin Resonance Study of Trapped Electrons in Gamma‐Irradiated Triethylamine Glasses

A study has been made of trapped electrons produced in γ‐irradiated triethylamine glasses at low temperature by electron spin resonance methods. A sharp singlet centered at g=2.003±0.001 was observed, which was readily bleachable with near‐infrared light. In the presence of an electron scavenger this singlet spectrum was not observed and it has been attributed to trapped electrons. The G value for the formation of trapped electrons has been estimated to be 0.5 at 77°K. Isothermal decay of trapped electrons at 77°K was found to be a first‐order process. Thermal decay measurements of trapped electrons indicated their rapid disappearance in a temperature region 105° to 112°K. A nuclear magnetic resonance study of a triethylamine glass revealed that motional narrowing in a resonance line of solvent protons occurred in about the same temperature region as that in which the rapid decay of trapped electrons was observed. The nature of the electron trap is briefly discussed.

Radiation-induced charge-transfer luminescence and its primary processes in toluene

Abstract Radiation-induced charge-transfer luminescence of several electron donor-acceptor systems was observed for the first time in toluene at room and low temperature. Observed spectra and fluorescence lifetime are almost the same as those obtained photochemically. The detailed analysis indicates the excitation transfer in the higher excited states of toluene et 77 K.