A Study of the Angular Dependence of Nuclear Resonance Fluoresence from Europium-152 in Glass and Crystal

Abstract

Nuclear effects are often used as analytical tools in atomic, chemical and biological studies. Radioisotope dating using naturally occurring isotopes can give the time elapsed since the object formed. The most common use of this type is the measurement of C-14 in organic matter. Often, unstable isotopes are used to label compounds to follow the course of the compound in a system. Nuclear magnetic resonance, measuring the strength of the interaction of nuclei with an external magnetic field, reveals information on the nuclei's environment. A way to measure very low concentrations uses a neutron source (commonly a nuclear reactor) to irradiate the sample. Some nuclei absorb a neutron and become unstable. These nuclei can then be identified from their gamma ray spectra. The Mossbauer effect uses nuclear resonance fluorescence, the absorption and reemission of gamma rays, as a very fine (~1 part in 10 10) time or energy filter for emitted gamma rays. Utilizing the fact that sometimes the entire crystal containing the decaying nuclei absorbs the recoil following emission of a gamma ray so that there is almost no recoil energy, the Mossbauer effect can reveal the Zeeman splitting of the nuclear energy states due to the magnetic field at the nucleus, allowing the field at the nucleus to be calculated. It would be desirable to have a similar technique capable of measuring the relative freedom of motion of a nucleus in its environment, that does not depend on the recoil being absorbed by the entire crystal. The rare earth isotope Europium-152 may provide this probe, allowing the determination of the shape of the potential energy well containing the rare earth atom. From this information further insight into the atomic interactions within the crystal may be gained.