A Tale of Two Compilations: Quadrupole Deformations and Internal Conversion Coefficients

Abstract

(i) The deformation of the nuclear ground state is a fundamental property that can be deduced in even-even nuclei from the B(E2) value for the first 2+ (21+) state. In 1987, we published a compilation of such B(E2: 01+→ 21+) values for ~ 280 even-even nuclei. Very recently, we have updated the 1987 compilation and have compared the adopted B(E2: 01+ → 21+) values (for ~ 330 even-even nuclei) with those given by various theoretical models (Finite-Range Droplet Model, Woods Saxon Model, Relativistic Mean-Field Calculations, Extended Thomas-Fermi Strutinski Integral Method, Hartree-Fock+BCS Calculations, and Dynamical Microscopic Model). Agreement between theory and experiment varies from “reasonable” to “excellent”.(ii) Currently, the most widely used Internal Conversion Coefficient (ICC) compilations are those by Hager and Seltzer, Rösel et al., and Band and Trzhaskovskaya. In all three cases, the calculation of electron wave functions is carried out in the framework of the Hartree-Fock-Slater (HFS) method. It has been suspected for some time that there is a “2–3% problem” — that is, the HFS models give results that are systematically larger than the experimental data by 2–3%. ICCs are now available from relativistic self-consistent Dirac-Fock (DF) calculations in which the exchange terms of DF equations are included exactly. The DF model gives results that are very close to the experimental data. The long-standing “2–3% problem” has apparently now been solved.