J. Witters

Electron spin resonance of single crystals of monoethylenediamine copper (II) sulfate

Abstract The E.S.R. in undiluted single crystals of copper(II) ethylene diamine sulfate has been investigated in the temperature range 300°K–4°K. In the plane perpendicular to the c axis the g-value was isotropic (2.063 ± 0.005) Along the c axis the g-value was 2.276 ± 0.005. The linewidth was found to be isotropic in all the planes investigated. g-factors and linewidth were independent of temperature within experimental error. An unusually high degree of exchange narrowing was also observed.

E.P.R. in neutron-irradiated DPPH

Abstract The influence of neutron irradiation of D.P.P.H., as measured by paramagnetic resonance at low temperatures is reported. The observed effects include a considerable increase in the number of spins and in the linewidth and a small but significant change in g -values.

Electron spin resonance studies of neutron-irradiated DPPH

Abstract The damages induced in solid crystalline DPPH, when neutron irradiated at liquid nitrogen temperature, is studied using the technique of paramagnetic resonance. A model is proposed which explains satisfactorily the observed variation in g-value, linewidth and spin concentration.

Paramagnetic Resonance in γ -Irradiated Donetz Coal

This chapter discusses the paramagnetic resonance in γ-irradiated Donetz coal. An X-band spectrometer has been adapted for recording narrow EPR absorption lines at temperatures from 300 to 2 K. In general the sample can be cooled by two different methods. One can put the sample in the narrow lower end of a dewar, and then introduce the dewar in the cavity. DPPH was used for calibration. It must be emphasized that there is a great inconvenience in using this substance as a reference in high fields. The line width and even the g-factor of DPPH depend too much on the preparation of the sample. It is found that for monocrystals anisotropy of the g-factor and the line width has been found resulting in a strong asymmetry of the line of a powdered sample. As a consequence the zero of the first Fourier component of the absorption signal, used in differential recording does not coincide with the top of χ, the deviation depending on the amplitude of the modulation field.

Bombardment of copper and germanium surfaces by low energy argon ions

SummaryPolycristalline copper surfaces and germanium single crystals were bombarded with 1000 eV argon ions. The argon ions were produced by means of an electron current between a heated tungsten cathode and an anode at a potential of +300 V. The pressure of the argon gas was maintained at 10−3 mm Hg. The whole system could be evacuated to 10−6 mm Hg with an oil diffusion pump.Before and after the bombardment, replica of the surface were made for investigation with the electron-microscope. After sputtering, dislocation steps appear at the surfaces, and the grain dimensions increase with increasing sputtering time. For the germanium single crystals, the dislocations seem to lie all in the same crystallographic direction.