α-cluster structure ofO18

Abstract

Background: Clustering phenomena in N = 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+α elastic scattering.Method: The Thick Target Inverse Kinematics (TTIK) technique was used to measure the excitation function for the 14 C+α 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 α-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 α-cluster strengths is observed in the spectrum of 18 O making the α-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.

Microscopic Theory of α-Particle Resonance Spectra

“…Otherwise, the calculated energy spectrum is consistent with the recent experimental findings. These encouraging results, as well as other successful applications of the CNCIM to heavier nuclei [10,11], compel us to make predictions and to take part in discussions related to interpretation of recent experimental data. The α decay widths predicted by CNCIM are summarized in the fourth column of Tab.…”

“…[10,11]. An important property of the new SFs is that they are normalized in that the sum of all SFs for a given partial wave l and to a particular daughter state equals to the number of channels involved.…”

“…Recent computational advances, development of the effective and ab-inito interaction Hamiltonians, as well as the ability to incorporate continua of reaction states bring the nuclear shell model to a new level. In this contribution we report progress in the development of the Cluster-Nucleon Configuration Interaction Model (CNCIM) [10,11] where we combine the CI technique with the Elliott's SU(3) group classification of cluster configurations. We apply CNCIM to study α clustering in 10 Be.…”

Quest for superradiance in atomic nuclei

“…Recent experiments [29,30,17] show that broad alpha-decaying states saturating the continuum coupling strength survive even in non self-conjugate (N = Z) nuclei such as 10 Be and 18 O, where extra valence nucleons make manybody dynamics extremely complex and permit multiple other open channels.…”

“…The data for 10 Be are taken from [16] and for 18 O from [17] continuum. In addition, many recent experiments [15,17,18] have demonstrated that cluster configurations remain intact despite being embedded in complex many-body dynamics. Cluster bands extend far into continuum and involve extremely broad states that do not share the alpha decay strength with the dense spectrum of other many-body states.…”