Influence of the density of states on the odd-even staggering in the charge distribution of the emitted fragments

TL;DR

This study investigates how the density of states influences odd-even staggering in charge distributions of nuclear fragments, revealing that pairing effects and excitation energy significantly impact observable patterns in fragmentation outcomes.

Contribution

The paper introduces a statistical model incorporating state densities with pairing gaps to analyze charge distribution patterns in nuclear fragmentation, highlighting the role of excitation energy and pairing effects.

Findings

Odd-even staggering diminishes with increasing excitation energy.

Pairing effects can enhance odd-even staggering in final yields.

Staggering effects are prominent in light systems at low energies.

Abstract

The fragmentation of thermalized sources is studied using a version of the Statistical Multifragmentation Model which employs state densities that take the pairing gap in the nuclear levels into account. Attention is focused on the properties of the charge distributions observed in the breakup of the source. Since the microcanonical version of the model used in this study provides the primary fragment excitation energy distribution, one may correlate the reduction of the odd-even staggering in the charge distribution with the increasing occupation of high energy states. Thus, in the frame- work of this model, such staggering tends to disappear as a function of the total excitation energy of the source, although the energy per particle may be small for large systems. We also find that, although the deexcitation of the primary fragments should, in principle, blur these odd-even effects as the fragments follow their decay chains, the consistent treatment of pairing may significantly enhance these staggering effects on the final yields. In the framework of this model, we find that odd-even effects in the charge distributions should be observed in the fragmentation of relatively light systems at very low excitation energies. Our results also suggest that the odd-even staggering may provide useful information on the nuclear state density.