Yukio Kurita

ELECTRON SPIN RESONANCE IN A GAMMA-IRRADIATED SINGLE CRYSTAL OF L-CYSTINE DIHYDROCHLORIDE

The electron spin resonance of a gamma‐irradiated single crystal of L‐cystine dihydrochloride, HOOC–CH–CH2–S–S–CH2–CH–COOH·2HCl,         –                             –        NH2                      NH2 has been measured at 9 kMc/sec and at 24 kMc/sec for various orientations of the crystal in the magnetic field. The resonance pattern was found to be a doublet, the spacing between the components of which is independent of the crystal orientation as well as of the strength of the static magnetic field. The spectroscopic splitting factor was found to be anisotropic with the principal values: gu=2.003, gv=2.025, and gw=2.053. A model of the free radical, HOOC–CH–CH2–S·,          –        NH2 in which the electron spin density is mainly concentrated in a nonbonding 3 p orbital of the sulfur atom, is proposed. The model accounts very well for the principal values of the g tensor as well as their directions relative to the atomic configuration. It also can give rise to the observed proton hyperfine structure.

Electron Spin Resonance Study of Radical Pairs Trapped in Irradiated Single Crystals of Dimethylglyoxime at Liquid‐Nitrogen Temperature

The ESR spectra of x‐irradiated single crystals of dimethylglyoxime have been measured at 77°K. An analysis of the spectra reveals that two paramagnetic species are produced by the irradiation. One is an iminoxy radical C(CH3)NOH–C(CH3)NO(M). The other, unstable at room temperature and containing two coupling nitrogen nuclei, is a radical pair with the mean distance between the two unpaired electrons of 5.6 A. The absorption corresponding to the ΔM=2 transition of the radical pair has been observed in polycrystalline samples. The radical pair is tentatively identified to be the one consisting of adjacent radicals M···M along the crystallographic a axis.

Electron Spin Resonance of an Irradiated Single Crystal of N‐Acetylglycine

Electron spin resonance absorption of an irradiated single crystal of N‐acetylglycine was observed at room temperature at 9 kMc and 12 kMc. From the analysis of the anisotropy in the spectroscopic splitting factor and in the nuclear hyperfine interaction constant, a chemical structure [Complex chemical formula] is deduced for the free radical. The C–H bond is in the NCC plane and approximately along the bisector of the NCC angle. The unpaired electron spin density is essentially in a π orbital, about 72% of which is the p orbital of the CH carbon directed perpendicular to the NCC plane.

ELECTRON SPIN RESONANCE IN A GAMMA-IRRADIATED SINGLE CRYSTAL OF THIODIGLYCOLIC ACID

The electron spin resonance of a gamma‐irradiated single crystal of thiodiglycolic acid was measured at room temperature at 9 kMc. From the analysis of the anisotropy in the spectroscopic spliting factor and in the nuclear hyperfine interaction constants, a model of the free radical HOOC–CH2–S–CH–COOH is proposed. In this free radical, the electron spin density is mainly in a π orbital, about 60% of which is the p orbital of the CH carbon, 2% is the 1s orbitals of the CH2 hydrogens, and 22% is in the p orbital of the S.

Electron Spin Resonance Study of Radical Pairs Trapped in X‐Irradiated Single Crystals of Dimethylglyoxime‐O,O‐d2, Glyoxime, and Methylglyoxime at Liquid‐Nitrogen Temperature

The ESR spectra of x‐irradiated single crystals of dimethylglyoxime‐O,O‐d2, glyoxime, and methylglyoxime have been measured at 77°K. An analysis of the spectra reveals the presence of radical pairs R1—CR2NȮ···R1—CR2NȮ , where R1=C(CH3)NOD and R2=CH3 for dimethylglyoxime‐d2 (the average distance between the unpaired electrons R=5.4 A), R1=CHNOH and R2=H for glyoxime (R≦4.8 A), and R1=CHNOH and R2=CH3 for methylglyoxime (R≦5.2 A). Radical pairs decay in dimethylglyoxime faster than in dimethylglyoxime‐d2. The fact shows that the iminoxy radicals CR1NOH–CR2NȮ diffuse by hydrogen‐atom abstraction from nearby hydroxyl groups.

Photochromism of a protonated 5-dimethylaminoindolylfulgide: a model of a non-destructive readout for a photon mode optical memory

The 5-dimethylaminoindolylfulgide–trichloroacetic acid (1 : 1.4) system in toluene was found to constitute a photochromic system having a non-destructive readout ability applicable to rewritable photon mode optical memories.

Electron Spin Resonance of Irradiated Single Crystals of ε-Caprolactam

ESR analyses of irradiated single crystals of epsilon caprolactam and well-resolved hyperfine couplings of N and H nuclei are reported. The spectrum has 24-line structure with 1H hyperfine couplings A(HIIe), A(HI ), A(HN), and 14N coupling A(N). The principal values of the hyperfine couplings and g factor are tabulated. Examination of the ESR spectra of the irradiated deuterated crystals confirmed that A(HN) is due to BETA - proton attached to the amide nitrogen atom.

ELECTRON SPIN RESONANCE OF RADICAL PAIRS IN X-IRRADIATED CLATHRATE COMPOUNDS OF HYDROQUINONE.

Abstract Electron spin resonance spectra of the X-irradiated clathrate compounds of hydroquinone with acetonitrile, sulfur dioxide, carbon dioxide, hydrogen chloride, methanol, and formic acid were studied at liquid nitrogen temperature. An ESR absorption spectrum due to a paramagnetic species in a triplet state was observed in each of these clathrate compounds. The analysis of angular dependence of the spectra for the complexes with acetonitrile and sulfur dioxide shows that this magnetic species is attributable to pairwise trapping of two p -hydroxyphenoxyl radicals about 5 A apart, an exchange interaction between them being responsible for the triplet state. An anomalous angular dependence of a spinlattice relaxation time was observed in the hydroquinone-acetonitrile clathrate compound. Cyanomethyl radicals were produced in the crystals of the hydroquinone-acetonitrile clathrate compound irradiated at low temperature and subsequently annealed at 190°K. These radicals undergo rapid rotational motion around the CC bond parallel to the c axis of the hexagonal crystal even at 77°K.

A New Effect of Ionizing Irradiation: Anisotropic Expansion of a Peptide Crystal

Expansion of crystals resulting from X irradiation was studied in the case of a peptide, N-acetyl-D, L-alanine. This expansion was discovered by examining several irradiated organic solids for possible expansion, which was suggested by the recent observation of crystal imperfections in another peptide. The expansion, which occurred anisotropically along the c axis, was found to depend on dose, the maximum being as large as 20% when assisted by heat treatment.

OPTICAL AND THERMAL CONVERSION OF V/sub k/ CENTERS IN X-IRRADIATED HYDROXYLAMMONIUM CHLORIDE.

The Cl 2 - centers trapped in X-irradiated single crystals of hydroxylammonium chloride have been studied by electron spin resonance technique in the temperature range from 77°K to 150°K. Two crystallographically inequivallent Cl 2 - centers designated as V k (I) and V k (II) are produced in the crystal. The former is composed of a chlorine ion pair situated on the b c plane and the latter is formed from a pair on the plane nearly perpendicular to the b c plane. Thermal conversion from V k (I) into V k (II) takes place thermally above 105°K and V k (II) is converted into V k (I) by irradiation with the V k light at 77°K.