Observation of Large Enhancement of Charge Exchange Cross Sections with Neutron-Rich Carbon Isotopes

TL;DR

This study measures nitrogen isotope production cross sections from high-energy carbon isotopes, revealing a significant enhancement for neutron-rich isotopes and suggesting a concentration of transition strength at low excitation energies.

Contribution

First measurement of nitrogen isotope production cross sections across a wide range of isotopes using high-energy carbon beams and charge measurements.

Findings

Cross sections increase rapidly with neutron number in projectiles.

Enhanced cross sections observed for neutron-rich isotopes in C-target data.

Data suggests low-energy concentration of Gamow-Teller and Fermi transition strength.

Abstract

Production cross sections of nitrogen isotopes from high-energy carbon isotopes on hydrogen and carbon targets have been measured for the first time for a wide range of isotopes. The fragment separator FRS at GSI was used to deliver C isotope beams. The cross sections of the production of N isotopes were determined by charge measurements of forward going fragments. The cross sections show a rapid increase with the number of neutrons in the projectile. Since the production of nitrogen is mostly due to charge exchange reactions below the proton separation energies, the present data suggests a concentration of Gamow-Teller and Fermi transition strength at low excitation energies for neutron-rich isotopes. It was also observed that the cross sections were enhanced much more strongly for neutron rich isotopes in the C-target data.