Angular Correlation Perturbed by an Anisotropic Hyperfine Interaction

Abstract
A theoretical investigation is made of the effect on a gamma-gamma angular correlation of the extranuclear pertubations which arise from the coupling between the magnetic dipole and electric quadrupole moments of the nucleus and the electromagnetic field of the electron shell in a paramagnetic crystal of axial symmetry. The hyperfine interaction is assumed to be time independent. Results are obtained for both single-crystal and polycrystalline sources. For a single-crystal source, the effect on the correlation of an external magnetic field parallel to the crystalline axis is investigated. The behavior of the correlation over the whole range of partially to fully decoupled nuclear and electronic spins is calculated. It is shown that under certain conditions an "angular correlation resonance experiment" is possible, i.e., an experiment in which the coincidence counting rate, for fixed positions of the detectors, exhibits sharp interference peaks as a function of the magnetic field. For a powder source, the attenuation factors are computed as a function of the hyperfine constants for arbitrary nuclear spin values. New possibilities for investigation of nuclear moments of excited states are discussed.

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