Bonn 2010 – wissenschaftliches Programm
HK 15.7: Vortrag
Dienstag, 16. März 2010, 15:30–15:45, HG II
The odd-even Z isospin anomaly in the yields from high-energy reactions — •M. Valentina Ricciardi1, Kalr-Heinz Schmidt1, Aleksandra Kelic-Heil1, and Beatriz Jurado2 — 1GSI - Helmholtzzentrum fuer Schwerionenforschung, Darmstadt, Germany — 2CENBG, Centre d'Etudes Nucleaires de Bordeaux-Gradignan, France
The odd-even Z isospin anomaly was discussed for the first time in 1999 by L.B. Yang et al., who observed this effect in the experimental production cross-sections of Ni+Ni and Fe+Fe at 75 A MeV. Since then, the analysis of experimental production cross-sections of final products of several nuclear reactions at very different energies confirmed the existence of this effect. In this talk we want to show that odd-even Z isospin anomaly is a direct consequence of the de-excitation process by particle evaporation occurring in the hot remnants of the nuclear reaction. In particular, the characteristics of the odd-even Z isospin anomaly can be reproduced providing that two effects are properly considered: the memory effects, which hold some reminiscences of the primary impinging nuclei, and the effect of pairing, which is responsible for the even-odd staggering in the yields. The latter correlates strongly with the lowest particle separation energy of the final experimentally observed nuclei, but it does not correlate with their binding energy, contrary to what at first one is tempted to think. Our study shows that it is precisely the memory effect combined with the characteristics of the lowest particle separation energy which determine the "isospin anomaly".