Static magnetic susceptibility measurements for 4°K < T < 300°K are reported for the following dioxygenyl salts: O2AsF6, O2SbF6, O2Sb2F11, and O2PtF6. In contrast to previous studies, we find both spin–orbit coupling and crystal field effects to be important. While the As and Sb compounds are paramagnetic at 4.2°K and have small O2+–O2+ exchange, O2PtF6 is ordered at 4.2°K, probably due to O2+–Pt(V) exchange. ESR studies confirm the susceptibility results, except in O2PtF6 where a resonance was not detected, and show that the O2+ magnetic state is described by an axial spin Hamiltonian with g⊥ ∼ 1.98 and g∥ ∼ 1.74. The ESR linewidth of O2AsF6 below 70°K is ∼ 80 G. Above 100°K the linewidth rapidly increases so that above 180°K the line is unobservable. This increase may be due to O2+ motion. NMR shows that the AsF6 groups in O2AsF6 are also rotating above 200°K, probably in some hindered form.
Irradiation of o~-A1203 (Corundum) was carried out in contact with acidic media and with different doses (100-to-2500 kGy) and dose-rates (0.9, 2.6 and 6.1 kGy.h 1) of y-rays. Simultaneously parallel experiments were carried out using the same procedure, but preheated at 150 ~ for two days and then irradiated without acidic media. The solid thus obtained was used to determine the effect of y-irradiation on the sorption capacities of microamounts of fission products from strongly alkaline aqueous solutions of uranium. The results revealed that the effect of y-irradiation of c~-A1203 and the acidic media in which it is immersed, is associated with a stable matrix resistant to significant changes in the composition of the surface layer; whilst it seems that the effect of y-irradiation of preheated c~-A1203, is connected with changes of surface OH groups strongly affected by heat treatment and irradiation dose.
The use of ionizing radiation to achieve some desired effect on silica gel, applicable to the adsorption of radionuclides has been investigated as a function of the dose-rate over a wide range of doses, in experiments with strongly alkaline aqueous solutions containing an excess of UO 2+ relative to trace concentrations of 88y, 103Ru ' 134Cs and 141Ce. The results obtained revealed that y-irradiation of silica gel was reproduced with an uptake comparable to that measured for the unirradiated-silica gel. Radiation resistance is strongly influenced by the basic macromolecular structure, the presence of water, and the particular environmental exposure conditions.
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