Analysis of fragment yield ratios in the nuclear phase transition

TL;DR

This study investigates the liquid-gas phase transition in nuclear reactions using the Landau free energy approach, revealing first-order transition signatures and verifying the order parameter relation through experimental yield ratios.

Contribution

It applies the Landau free energy framework to nuclear fragmentation data, demonstrating the first-order phase transition and experimentally confirming the order parameter relation in nuclear systems.

Findings

Evidence of three minima in free energy indicating first-order phase transition.

Experimental verification of the order parameter relation from yield ratio data.

Systematic decrease of the slope parameter with increasing excitation energy.

Abstract

The critical phenomena of the liquid-gas phase transition has been investigated in the reactions 78,86Kr+58,64Ni at beam energy of 35 MeV/nucleon using the Landau free energy approach with isospin asymmetry as an order parameter. Fits to the free energy of fragments showed three minima suggesting the system to be in the regime of a first order phase transition. The relation m =-{\partial}F/{\partial}H, which defines the order parameter and its conjugate field H, has been experimentally verified from the linear dependence of the mirror nuclei yield ratio data, on the isospin asymmetry of the source. The slope parameter, which is a measure of the distance from a critical temperature, showed a systematic decrease with increasing excitation energy of the source. Within the framework of the Landau free energy approach, isoscaling provided similar results as obtained from the analysis of mirror nuclei yield ratio data. We show that the external field is primarily related to the minimum of the free energy, which implies a modification of the source concentration \Delta used in isospin studies.