Feature Articles: A Relativistic Symmetry in Nuclei

Abstract

IntroductionMore than thirty years ago it was observed that certain quantum energy levels in atomic nuclei were almost degenerate in energy [1]. The states that are almost degenerate (quasi-degenerate) have different radial quantum numbers and different orbital angular momenta, features that made the reason for their degeneracy difficult to penetrate.The dynamics of neutrons and protons in nuclei have been successfully treated non-relativistically. Therefore it has come as a surprise that this quasi-degeneracy of quantum states in heavy nuclei, which has eluded understanding for about thirty years, can be explained by a relativistic symmetry [2].