Nuclear Data Sheets for A = 229

Abstract

The evaluators present in this publication spectroscopic data and level schemes from radioactive decay and nuclear reaction studies for all nuclei with mass number A = 229. These nuclei belong to a region of coexisting quadrupole with possible octupole deformations. The latter have been observed in 229Ra, but in 229Pa the experimental evidence is inconclusive. The present evaluation of A = 229, which includes all data received by June 2008, supersedes the 1989 evaluation by Y.A. Akovali, published in Nuclear Data Sheets 58, 555 (1989). Highlights of this publication are given below: A comprehensive spectroscopic study of 229Fr(50.2 s) β- decay using mass-separated sources have provided the first evidence of parity doublets in 229Ra due to nuclear octupole deformation (1999Fr33). In 229Th a level at 7.6 5 eV – the closest level to the ground state ever known – has been confirmed through extremely precise measurements of γ-ray energies from 233U α decay (1994He08, 2007Be16). A nuclear level at such low energy may be used for studying a large variety of atomic properties associated to nuclear decay. The level structure in 229Pa has been interpreted in terms of the rotational model (1994Le22). Some authors, however, have proposed the existence of parity doublets as evidence of octupole nuclear deformation (1982Ah08). This interpretation has not been confirmed.