Eur. Phys. J. A (2006) 29: 133-139
https://doi.org/10.1140/epja/i2006-10076-x

Nuclear Structure and Reactions

Dynamics of α-clusters in N = Z nuclei

¹ Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, D-14195, Berlin, Germany
² Hahn-Meitner-Institut Berlin, Glienicker Strasse 100, D-14109, Berlin, Germany

^* e-mail: oertzen@hmi.de

Received: 11 May 2006
Accepted: 31 July 2006
Published online: 1 September 2006

Abstract

The systematics for binding energies per α-particle in N = Z nuclei, E _Bα/N _α, are studied up to ¹⁶⁴Pb. It is shown that, although a geometrical model can be used to explain the systematics for light nuclei, the binding energy per α-particle exhibits structures which are due to the well-known shells of the mean field of nucleons in nuclei. The overall dependence of E _Bα/N _α on N _α in N = Z nuclei (for the ground-state masses) can be described in a liquid-drop model of α-particles. Conditions for a phase change with the formation of an α-particle condensate, a dilute Bose gas in excited compound nuclei are discussed for E _Bα/N _α = 0, at the thresholds. This is achieved when the binding energy per nucleon in nuclei is equal to or smaller than in the α-cluster. At somewhat smaller excitation energies the appearance of a Bose gas with a closed-shell core (N = Z, e.g. of ⁴⁰Ca) is proposed within the same concept. The experimental observation of the decay of such condensed α-particle states is proposed with the coherent emission of several correlated α-particles not described by the Hauser-Feshbach approach for compound-nucleus decay. This decay will be observed by the emission of unbound resonances in the form of ⁸Be and ¹²C ^* (0⁺ ₂) clusters.