R. W. Reynolds

Ground‐State Splitting of Trivalent Gd and Cm in ZrSiO4, HfSiO4, and ThSiO4, Determined by ESR

The electron spin resonance spectrum of trivalent gadolinium impurity in the tetragonal host crystals of ZrSiO4, ThSiO4, and HfSiO4 has been observed at X band, and the spin‐Hamiltonian parameters were obtained at various temperatures. The dominant second‐order parameter B20 for Gd was observed to be negative in all three crystals. Hyperfine structure for the odd isotopes 155Gd and 157Gd was clearly resolved and measured. In ThSiO4 crystals doped with trivalent curium, no ESR signals were detected, supporting the assumption of a large negative B20 term for this ion in these hosts.

Gd3+ ESR Spectra in Cubic and Trigonal Sites of BaF2

Accurate spin‐Hamiltonian parameters for Gd3+ in cubic and trigonal sites of BaF2 have been determined at 300, 77, and 4.2°K. Previously undetermined signs of the crystal‐field constants were established. Unusual linewidth and intensity variations were observed in the BaF2:Gd3+ trigonal spectrum.

EPR determination of the nuclear spins and magnetic moments of 243Cm and 247Cm

Abstract EPR spectroscopy has been employed in making the first direct measurements of the nuclear spins of 243 Cm and 247 Cm ( I = 5 2 and I = 9 2 respectively). Estimated nuclear moments are |0.4μ N | for 243 Cm and |0.36 μ N | for 247 Cm.

Electron Spin Resonance Spectra of Er3+ and Yb3+ in Single Crystals of SrCl2

The ESR spectra of Yb3+ and Er3+ in cubic sites of SrCl2 (Fluorite structure) have been observed at a frequency of 10 Gc/sec and at 4.2° and 20°K. The spectra were isotropic with g = 3.417 ± 0.001 for Yb3+ and g = 6.754 ± 0.005 for Er3+ indicating that a Γ7 doublet is the ground state in both cases. The Er3+ Γ7 ground state shows that a large variation in the B4 / B6 ratio consistent with the point‐charge model is not present in the more inflated SrCl2 lattice relative to other fluorite‐type hosts. The Yb3+Γ7 ground state is in agreement with previous measurements on Yb3+ in eightfold coordinated cubic sites and no behavior inconsistent with predictions of the point‐charge model was in evidence. Hyperfine structure was resolved with A(171Yb) = 881 ± 1 × 10−4cm−1, A(173Yb) = 242.9 ± 0.3 × 10−4cm−1, and A(167Er) = 233.5 ± 0.3 × 10−4cm−1. Axial spectra were also observed but not measured due to their low intensity and linewidth variation with magnetic‐field orientation.