Isotopic Dependence of the Caloric Curve

TL;DR

This study investigates how isotopic composition affects the caloric curve in projectile fragmentation at relativistic energies, finding that chemical freeze-out temperatures are nearly independent of isotopic ratios, which supports certain microscopic model predictions.

Contribution

The paper provides experimental evidence that chemical freeze-out temperatures are invariant across different isotopic compositions, challenging some interpretations of limiting temperatures.

Findings

Freeze-out temperatures are nearly invariant with isotopic composition.

Results support microscopic model predictions of limiting temperatures.

Isotopic effects have minimal impact on the caloric curve in projectile fragmentation.

Abstract

Isotopic effects in projectile fragmentation at relativistic energies have been studied with the ALADIN forward spectrometer at SIS. Stable and radioactive Sn and La beams with an incident energy of 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z ratio of the produced spectator sources, consistent with predictions for expanded systems. Consequences for the proposed interpretation of chemical breakup temperatures as representing the limiting temperatures predicted by microscopic models are discussed.