N/Z influence on the level density parameter

G Ademard,M.-F Rivet,B Borderie,T Twarog,P Marini,L Augey,N Le Neindre

doi:10.1051/epjconf/20158800030

Abstract

A completely exclusive experiment was performed by the INDRA collaboration to study the isospin dependence of the level density parameter. Over a large N/Z range, the fusion-evaporation charged products of 34,36,40 Ar+ 58,60,64 Ni reactions were measured and identified both in charge and mass by coupling INDRA and VAMOS spectrometer. Preliminary results obtained by combining data of both detectors are presented for the 36 Ar+ 58 Ni at 13.3 A MeV. The analysis method of relevant observables for such an ambitious investigation are discussed and the progress of the data analysis are reviewed.

Highlights

Being able to describe the competition among the various decay modes of excited nuclei has been one of the main goals of research in nuclear physics
It is involved in several aspects of nuclear reactions, for instance in statistical models used in nuclear physics, astrophysics and in the search for superheavy elements
Before the data can be analysed for physics, it is necessary to have a good calibration for both INDRA and VAMOS detectors

Summary

Introduction

Being able to describe the competition among the various decay modes of excited nuclei has been one of the main goals of research in nuclear physics. In the multifragmentation process observed at Fermi energies, excited neutron deficient fragments are assumed to be formed, and their de-excitation is not well constrained [2] This expression is obtained within a single particle model and used in most statistical model calculations. The effective nucleon mass is expected to decrease with increasing temperature T while T ≤2 MeV This implies a decrease of the level density parameter and an increase of the kinetic symmetry energy contribution to the nuclear binding energy Esym(T ) = bsym(T ) × (N − Z)2/A as T increases. The fundamental goal is to explore the variation of de-excitation properties and level density parameters with the N/Z of the compound nucleus when going from the proton-drip line to stable nuclei. We can test the influence of the mass asymmetry of the entrance channel on the different components of the fusion cross section (ER, fission . . . )

The studied systems

Experimental set-up

Analysis plan

Present status of the project

Findings

Conclusion