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The electron spin resonance of the Gd3+ ion has been studied in two series of glasses having the molar compositions 6SiO2:5Na2O: x (Gd2O3 + Y2O3) with 0 ≤ x ≤ 0.5 and 500SiO2: x Na2O:1Gd2O3 with 2.5 ≤ x ≤ 494. The spectra were nearly independent of temperature and sample composition, but varied strongly with microwave frequency in the range 5.4–38.4 GHz. The data were interpreted in terms of the spin Hamiltonian for a strong cubic crystal field and also in terms of the usual rhombic spin Hamiltonian H = g 0β H · S + D[Sz2 − (1/3)S  (S + 1)] + E(Sx2 − Sy2) with S = (7/2). Computer calculations were made yielding all possible effective g values for this latter Hamiltonian for all physically distinct combinations of the crystal field parameters when the Zeeman field H was restricted to the x, y, or z direction. The resonance features were related to three distinct sites for the Gd3+ ion. The spectra are indicative of a chemically heterogeneous glass matrix composed of soda-rich, silica-rich, and diffuse transition regions. The heterogeneities were found to exist over the entire range of compositions studied. Variations in the resonance intensity associated with the soda-rich region suggest the existence of a very well-defined substructure within the region. The data indicate that the substructure is related to the fundamental structural features of the possible crystalline compounds which can exist within the composition range.

Measurements are reported of the magnitude and asymmetry of the ring deuteron quadrupole coupling tensor in several simple deuterated benzene derivatives, i.e., benzene, toluene, ethylbenzene, as well as naphthalene, pyridine, and cyclohexane, using polycrystalline specimens at 77°K and in a magnetic field strength of 24 kOe. The e2qQ/h and '1 values obtained are: benzene, 180.7±1.5 kHz, 0.041±0.OO7; toluene, 179.9±1.7 kHz, 0.056±0.OO2; ethylbenzene, 177.8±2.2 kHz, 0.063±0.OO3; pyridine, 178.0±1.2 kHz, 0.039±0.OO6; cyclohexane, 173.7±1.7 kHz, ~0.01; naphthalene, 176.7±1.5 kHz, 0.053±0.OO5.

Nuclear magnetic resonance measurements of the 45 Sc, 1 H, and 2 D spin-lattice relaxation rates in the solid solutions ␣-ScH x (xϭ0, 0.11, and 0.27͒ and ␣-ScD x (xϭ0.05 and 0.22͒ have been performed over the temperature range 4.2-294 K. For the hydrided and deuterided samples we have found pronounced deviations of the 45 Sc relaxation rate measured at 86.2 MHz from the Korringa behavior in the range 30-180 K. The excess 45 Sc relaxation rate displays a peak near 100 K in ␣-ScH x and near 110-140 K in ␣-ScD x , resulting from the quadrupole interaction modulated by fast localized hopping of H͑D͒ atoms. The amplitude of the 45 Sc relaxation rate peak in the deuterided samples is found to be much higher than in the hydrided samples with comparable hydrogen content. This unusual isotope effect indicates that the fraction of D atoms participating in the fast localized motion in ␣-ScD x is approximately six times as large as the corresponding fraction of H atoms in ␣-ScH x . The results of our measurements of the 1 H and 2 D relaxation rates are consistent with this conclusion. The strong effect of H↔D substitution on the fraction of atoms involved in the localized hopping should be accounted for in any microscopic model of hydrogen motion in Sc. ͓S0163-1829͑99͒15725-4͔

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Electronic shielding by closed electron shells has been investigated in salts of trivalent thulium, by measuring the temperature dependence of the nuclear quadrupole splitting of the 8.42-keV gamma transition in Tm 169 . The measurements were performed by using the technique of recoilless nuclear resonance absorption. The nuclear quadrupole interaction was studied for Tm 3+ ions in thulium ethyl sulfate, thulium oxide, and thulium trirluoride within a temperature range from 9.6 to 1970°K. The interpretation of the experimental data in terms of the contributions of distorted closed electron shells to the quadrupole interaction yields values for electronic shielding factors. The results lead to amounts of 10% or less for the atomic Sternheimer factor RQ. The experiments also reveal substantial shielding of the 4/ electrons from the crystal electric field, expressed by the shielding factor 0-2. Values of 250 and 130 are obtained for the ratio {\~y^)/{\-0-2) for thulium ethyl sulfate and thulium oxide, respectively, where Y M is the lattice Sternheimer factor.