Eur. Phys. J. A 16, 313-329 (2003)
DOI: 10.1140/epja/i2002-10105-x

Beta-decay of the nucleus

I. Piqueras^{1, 2}, M.J.G. Borge¹, Ph. Dessagne², J. Giovinazzo², A. Huck², A. Jokinen³, A. Knipper², C. Longour², G. Marguier⁴, M. Ramdhane³, V. Rauch², O. Tengblad^{1, 3}, G. Walter², Ch. Miehé² and the ISOLDE Collaboration<sup>3

1</sup>  Instituto de Estructura de la Materia, CSIC, Serrano 113bis, E-28006 Madrid, Spain
²  Institut de Recherches Subatomiques, UMR 7500 CNRS-IN2P3 et Université Louis Pasteur, 23 rue du Loess, B.P. 28, F-67037 Strasbourg Cedex 2, France
³  ISOLDE, Division EP, CERN CH-1211 Geneva, Switzerland
⁴  Institut de Physique Nucléaire, Université Claude Bernard-Lyon I, F-69622 Villeurbanne Cedex, France

borge@pinar2.csic.es

(Received: 7 February 2002 / Revised version: 14 October 2002 / Published online: 6 March 2003)

Abstract
The beta-decay of the N=Z, even-even nucleus has been studied at the ISOLDE PSB facility at CERN. Measurements of and coincidences have enriched the decay scheme of the daughter nucleus with 27 new low spin levels. A more precise half-life of T_1/2=17.1(2) s has been determined. Strong feeding to the ground state is established yielding an unambiguous = 1 ⁺ assignment for this state. Candidates for the g.s. wave function are discussed in the framework of a self-consistent deformed mean-field calculation with SG2 Skyrme force and pairing correlations. A search for beta-delayed particle emission was made and an upper limit of 10 ^-6 for this decay branch obtained. The cumulated experimental level density of 1 ⁺ states has been fitted with the constant temperature formula. The comparison indicates that most likely all 1 ⁺ levels up to 1.2 MeV have been observed in this investigation. The corresponding nearest-neighbour level spacing does not follow a Poisson distribution. The Gamow-Teller strength distribution is compared, in terms of nuclear deformation, with different calculations made in the framework of the quasiparticle random phase approximation.

PACS
21.10.Hw - Spin, parity, and isobaric spin.
23.20.Lv - Gamma transitions and level energies.
23.40.Hc - Relation with nuclear matrix elements and nuclear structure.
27.50.+e - .

© Società Italiana di Fisica, Springer-Verlag 2003