Influence of additional neutrons on the fusion cross-section beyond the N=8 shell

TL;DR

This study investigates how additional neutrons influence the fusion cross-section of oxygen isotopes with carbon, revealing unexpected variations in fusion behavior for odd isotopes that challenge existing theoretical models.

Contribution

It provides new experimental data on neutron-rich oxygen isotopes' fusion cross-sections and highlights discrepancies with current theoretical predictions.

Findings

Fusion cross-section for even isotopes is consistent.

Odd isotopes show enhanced or suppressed cross-sections.

Theoretical models do not match experimental results.

Abstract

Fusion enhancement for neutron-rich isotopes of oxygen on carbon nuclei was probed. To measure the fusion cross-section a $^{20}$O beam accelerated to E$_{lab}$/A=2.7 MeV bombarded the active-target detector MuSIC@Indiana with a fill gas of CH$_4$. Examination of the average fusion cross-section over the interval 12 MeV $\leq$E$_{c.m.}$$\leq$ 17 MeV for $^{16-20}$O + $^{12}$C reveals that while even isotopes of oxygen exhibit essentially the same cross-section, the cross-section for odd isotopes can be either enhanced or suppressed relative to the even A members of the isotopic chain. Theoretical models fail to explain the observed experimental results.