D. Henzlovaa, M. V. Ricciardia, J. Benlliureb, A. S. Botvinaa, T. Enqvista, A. Kelic a, P. Napolitania, J. Pereirab, K.-H. Schmidta

1
Investigation of the N/Z of the heavy
fragmentation products the isospin thermometer
method
D. Henzlovaa, M. V. Ricciardia, J. Benlliureb,
A. S. Botvinaa, T. Enqvista, A. Kelic a, P.
Napolitania, J. Pereirab, K.-H.
Schmidta aGSI-Darmstadt, Germany bUniv.
Santiago de Compostela, Spain
2
Motivation

• investigation of the properties of the nuclear
  matter under extreme conditions (E, density,
  isospin)

understanding the supernovae explosions,
formation and stability of neutron stars

• onset of rapid disintegration of nucleus
  observed for high E

nuclear caloric curve
liquid-gas phase transition in NM

• measurements of temperature

information from IMFs and light fragments only
Tfreeze-out from these methods 5MeV
J. Pochodzalla et al., Phys. Rev. Lett. 75 (1995)
1040

• extension of the thermometry towards the heavy
  fragments

3
Important issues

• disturbing effect of evaporation

• full isotopic identification

the FRagment Separator (FRS)
evaporation residue corridor
208Pbd 1AGeV
properties of nuclei after long evaporation
largely universal
4
Systematic investigation of ltNgt/Z of heavy
fragmentation products
fission excluded!
T.Enqvist, et al. Nuc. Phys. A658 (1999) 47
T.Enqvist, et al. Nuc. Phys. A703 (2002) 435
M.V.Ricciradi, et al. proc. of XXXI Hirschegg
Workshop, Jan. 2003

• final fragments keep higher ltNgt/Z than the EPAX
  prediction

lack of excitation energy at the beginning of
evaporation

• final fragments scale with the N/Z of the
  projectile

long evaporation process keeps a memory on the
initial N/Z of the system
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Interpretation of the data

• two stage process

abrasion
evaporation
excited prefragment

• E deposited in the prefragment by far exceeds
  the E corresponding to T5MeV

ABRABLA calculation
238UPb 1 AGeV

• possible scenario

evaporation
abrasion
break-up
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Understanding the observed features - the isospin
thermometer method

• the isospin thermometer method explores the
  reduction of N/Z in evaporation process to
  restore the E after break-up

access to the fragment temperature at the
freeze-out of the break-up stage
abrasion
break-up
238U
upper limit of Tfreeze-out 5.5 MeV
evaporation
136Xe
Preliminary
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Summary

• FRS allows to extend the full isotopic
  identification up to the mass

of the projectile

• FRS data for neutron rich projectiles

final fragments after evaporation still keep an
important information about the reaction mechanism

• high E introduced and observed deviation of the
  heavy fragmentation residues from the EPAX
  prediction signals a break-up process in their
  formation

evaporation process tool to access the
freeze-out of the break-up stage
freeze-out temperature deduced from heavy
residues in accord with IMFs investigations