Shozo Kubota

Anisotropic hyperfine interaction in the electron spin resonance spectrum of the methyl radical trapped in CH3COONa⋅3D2O crystal at low temperatures

The electron spin resonance spectrum of the methyl radical produced by γ irradiation of CH3COONa⋅3D2O single crystal at 77 K has been measured at low temperatures. The spectrum observed at below 24 K consisted of eight lines with approximately equal intensities, instead of the four lines (1:3:3:1) at higher temperatures, due to the quantum tunneling of the rotational states. The transitions at low temperatures were angular dependent upon the applied field. From the analyses of the angular dependence of the spectrum with the aid of the theoretical calculation of the transition field for the tunneling methyl radical, the following anisotropic hyperfine tensor for the proton was determined (MHz): Axx=−31.4, Ayy=−93.7, Azz=−60.3, a (iso) =−61.8. These parameters provide the first experimental assessment of the well‐known theoretical results on the proton hyperfine anisotropy in the free methyl radical.

An improved insertion‐type liquid‐helium Dewar for X‐band ESR spectroscopy

A liquid‐helium Dewar in conjunction with the X‐band room‐temperature cavity is reported. The Dewar consists of a fourfold silvered Pyrex glass tube graded to fourfold unsilvered clear fused quartz fingers. A full charge (250 ml) of liquid helium has given about 10 h of operation.

Electron spin relaxation of methyl radicals in alkali metal acetates

Abstract The hyperfine splitting constant of the methyl radical, produced by the γ-irradiation of alkali metal acetates, decreases from that found in caesium acetate in the order potassium, sodium and lithium. Electron spin relaxation is also affected by the presence of alkali metals, showing some correlation with the changes in the hyperfine splitting constants. It is estimated that the intramolecular anisotropic dipolar interaction between the unpaired electron and the magnetic moment of the protons may be a major mechanism contributing to the electron spin relaxation, and that the variation in T1T2 values among the metal acetate systems may be attributed to the freedom of molecular motion of the methyl radicals in the metal acetates.