The Caloric Curve of Hot Nuclei

Abstract

The symmetric system Au + Au was studied over a wide range of incident energies. At energies above 600 A-MeV the decay of spectator nuclei emerging from semiperipheral collisions was investigated and at energies between 50 and 200 A-MeV that of the interaction region formed in central collisions. Temperatures were derived from several double-ratios of neighboring isotopes and from the population of excited states in ⁵Li and ⁴He. Agreement was found among the different isotope temperatures and also among the two excited state temperatures. The comparison of isotope and excited state temperatures, however, reveals large differences.

The excitation energies deposited in the spectator nuclei were determined via calorimetry. The observed dependence of the energy spectra of neutrons on the incident energy disagrees with the universality of spectator decay and indicates preequilibrium contributions.

for the ALADIN-collaboration: R. Bassini², M. Begemann-Blaich¹, Th. Blaich³, H. Emling¹, A. Ferrero², S. Fritz¹, S.J. Gaff⁸, C. Groß¹, G. Immé⁴, I. Iori², U. Kleinevoß¹, G. J. Kunde⁸†, W. D. Kunze⁵, V. Lindenstruth² , M. Mahi¹, T. Möhlenkamp⁶‡, A. Moroni², W. F. J. Müller¹, C. Nociforo⁴, B. Ocker¹, T. Odeh¹, F. Petrucelli², J. Pochodzalla^1§, G. Raciti⁴, G. Riccobene⁴, A. Saija⁴, F.P. Romano⁴, Th. Rubehn^1‡, H. Sann¹, M. Schnittker¹, A. Schüttauf⁵, C. Schwarz¹, W. Seidel⁶, V. Serfling¹, S. Sfienti⁴, J. Stroth¹, W. Trautmann¹, A. Trzcinski⁷, G. Verde⁴, A. Wörner¹, H. Xi^8‡, E. Zude¹, B. Zwieglinski⁷ 1 Gesellschaft für Schwerionenforschung, D-64291 Darmstadt, Germany 2 Dipartimento di Fisica, Università di Milano and I.N.F.N., I-20133 Milano, Italy 3 Institut für Kernchemie, Universität Mainz, D-55099 Mainz, Germany 4 Dipartimento di Fisica dell’ Università and I.N.F.N., I-95129 Catania, Italy 5 Institut für Kernphysik, Universität Frankfurt, D-60486 Frankfurt, Germany 6 Forschungszentrum Rossendorf, D-01314 Dresden, Germany 7 Soltan Institute for Nuclear Studies, 00-681 Warsaw, Hoza 69, Poland 8 NSCL, Michigan State University, East Lansing, MI 48824, USA † Present adress: Department of Physics, Yale University, New Haven CT 06512, USA ‡ Present adress,NSCL, Michigan State University, East Lansing, MI 48824, USA § Present address: Max Planck Institut für Kernphysik, Heidelberg, Germany