Structural effects in the nuclide distributions of the residues of highly excited systems

TL;DR

This paper reports new experimental data showing even-odd staggering effects in isotope production cross-sections from high-energy nuclear reactions, linked to nuclear structural effects in level densities.

Contribution

It provides novel measurements of nuclide distributions in highly excited systems, revealing structural effects influencing residue yields.

Findings

Strong even-odd staggering in isotope chains

Enhanced effects at N=Z

Reversal in neutron-rich odd-A residues

Abstract

New data from GSI on the production-cross-section for fragmentation of the systems 56Fe+p and 56Fe+Ti at 1 A GeV revealed the appearance of even-odd staggering in the cross-section distribution for chains of isotopes with given N-Z. The staggering is strongly enhanced for the chain N=Z, it reduces as the production moves away from the N=Z chain, and it reverses for the most neutron-rich odd-A residues. These phenomena, observed in the residues of rather violent reactions, are related to structural effects in the level-densities below the particle-emission threshold.