Production of neutron-rich heavy residues and the freeze-out temperature in the fragmentation of relativistic 238U projectiles determined by the isospin thermometer

Isotope yields of heavy residues produced in collisions of U-238 with lead at 1 A GeV show indications for a simultaneous break-up process. From the average N-over-Z ratio of the final residues up to Z = 70, the average limiting temperature of the break-up configuration at freeze out was determined to T approximate to 5 MeV using the isospin-thermometer method. Consequences for the understanding of other phenomena in highly excited nuclear systems are discussed. (C) 2002 Elsevier Science B.V. All rights reserved.