Fifty Years of Nuclear Quadrupole Moments

Abstract

On March 2, 1935 Hermann Schüler and Theodor Schmidt reported the first experimental evidence of non-spherical nuclei. From careful hyperfine structure studies of several Eu I-lines, they had shown that the hyperfine components of 151Eu and 153Eu did not follow the Lande interval rule exactly. Since the deviations were larger for 153Eu with the smaller magnetic moment, level perturbations were ruled out. This led to the conclusion of nuclear quadrupole moments. The theory was published June 1, 1935 by Hendrik B. G. Casimir. Nuclear deformations are playing a decisive role in modern nuclear structure physics. For solid state physics, spectroscopic quadrupole moments are very useful, since they probe the electric field gradient at the nuclei. This review presents the discovery of 1935 in historical context: 1. Early measurements of nuclear radii. 2. Discovery of nuclear quadrupole moments. 3. Spectroscopic quadrupole moments (absolute measurements; relative hyperfine data, europium revisited). 4. Intrinsic quadrupole moments (discovery from isotope shifts; present status, samarium revisited). 5. Charge distribution of deformed nuclei. © 1986, Verlag der Zeitschrift fur Naturforschung. All rights reserved.