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

Abstract Isotope yields of heavy residues produced in collisions of 238 U 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 ≈5 MeV using the isospin-thermometer method. Consequences for the understanding of other phenomena in highly excited nuclear systems are discussed.