Nuclear Charge Radii

Abstract

Nuclei are experimentally observed to have charge radii that show remarkably different trends to those that may be naively expected from liquid drop or droplet behavior. Instead, its variation with proton and neutron numbers exhibits diverse patterns that offer a unique insight into the structure of atomic nuclei and fundamental symmetries. The techniques developed to measure nuclear charge radii during the last 50–70 years have become increasingly sensitive and are nowadays applied to determine differential changes throughout the nuclear landscape from the lightest to the heaviest elements. While elastic electron scattering and muonic-atom spectroscopy has been applied almost exclusively to stable isotopes, optical and particularly laser spectroscopy has become a unique tool to gain insight into the behavior of nuclear charge radii along isotopic chains of short-lived isotopes. Collinear laser spectroscopy and resonance ionization spectroscopy are the workhorses for these studies and have already been applied to a significant fraction of the nuclear chart. This chapter will provide an overview on the techniques that are used to determine nuclear charge radii and a selection of results from different regions of the nuclear chart to highlight some of the unique phenomena exhibited by this fundamental property.