$\alpha$-cluster structure of $^{18}$O

TL;DR

This study investigates the alpha-cluster structure of $^{18}$O through experimental resonance measurements and theoretical modeling, revealing complex fragmentation patterns that differ from those in $N=Z$ nuclei.

Contribution

It provides detailed spectroscopic data and compares experimental results with cluster-nucleon configuration interaction model calculations for $^{18}$O.

Findings

Strong fragmentation of alpha-cluster strength in $^{18}$O

Distinct alpha-cluster structure from $N=Z$ nuclei

Experimental data on spin-parities and decay widths

Abstract

Background: Clustering phenomena in $N \neq Z$ nuclei provide an opportunity to understand the interplay between cluster and nucleon degrees of freedom. Purpose:To study resonances in the $^{18}$O spectrum, populated in $^{14}$C+$\alpha$ elastic scattering. Method: The Thick Target Inverse Kinematics (TTIK) technique was used to measure the excitation function for the $^{14}$C+$\alpha$ elastic scattering. A 42 MeV $^{14}$C beam was used to populate states of excitation energy up to 14.9 MeV in $^{18}$O. The analysis was performed using a multi-level, multi-channel R-Matrix approach. Results: Detailed spectroscopic information, including spin-parities, partial $\alpha$- and neutron- decay widths and dimensionless reduced widths, was obtained for excited states in $^{18}$O between 8 and 14.9 MeV in excitation energy. Cluster-Nucleon Configuration Interaction Model calculations of the same quantities are performed and compared to the experimental results. Conclusions: Strong fragmentation of large $\alpha$-cluster strengths is observed in the spectrum of $^{18}$O making the $\alpha$-cluster structure of $^{18}$O quite different from the pattern of known quasi-rotational bands of alternating parity that are characteristic of $N=Z$, even-even nuclei like $^{16}$O and $^{20}$Ne.