Structure of Ne20 states in resonance O16+α elastic scattering

Abstract

Background: The nuclear structure of the cluster bands in 20 Ne presents a challenge for many theoretical approaches. It is especially difficult to explain the broad 0 + and 2 + states, both at around 9 MeV excitation energy. More reliable experimental data for these levels is important for proper quantitative assessment and development of theoretical methods.Purpose: To obtain new data on 20 Ne α-cluster structure.Method: Thick target inverse kinematics technique was used to study the 16 O+α resonance elastic scattering and the data were analyzed using an R-matrix approach. The 20 Ne spectrum, the cluster and nucleon spectroscopic factors were calculated using cluster-nucleon configuration interaction model (CNCIM). Conclusions: Our experimental results obtained by the TTIK method generally confirm the adopted data on α cluster levels in 20 Ne. The CNCIM gives a good description of the 20 Ne positive parity states up to an excitation energy of ∼ 7 MeV, predicting reasonably well the excitation energy of the states and their cluster and single particle properties. At higher excitations, a qualitative disagreement with the experimentally observed structure is evident, especially for broad resonances.

Quest for superradiance in atomic nuclei

“…3 we summarize some recent interesting results related to clustering in 20 Ne, see Ref. [18]. The ground state rotational band is well reproduced in theoretical calculations using an sd model space, Ref.…”

“…These broad resonances cannot be described by the two theoretical approaches discussed here, nor they can be described by several more extended approaches addressed in Ref. [18]. Their broad nature suggests a superradiance mechanism and collectivization that is difficult to capture with the traditional shell model that does not include continuum.…”

“…3 the agreement between theory and experiment for these three bands is very good. However, recent studies [18] show the existence of a superradiant cluster rotational band that includes two broad resonances around 9 MeV of excitation (shown in red in Fig. 3).…”

“…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.…”