Systematics of alpha-chain states in 4N-nuclei

doi:10.1016/0375-9474(92)90089-3

Nuclear Physics A

Volume 549, Issue 3, 16 November 1992, Pages 431-438

https://doi.org/10.1016/0375-9474(92)90089-3 Get rights and content

Abstract

Recently a six-alpha chain state has been discovered in ²⁴Mg. The Bloch-Brink cranked cluster model shows that linear chains of alpha particles are associated with stable minima in the potential-energy surface for all 4N-nuclei. Experimental candidates in ⁸Be, ¹²C and ¹⁶O have already been identified. Using a Brink-Boeker effective interaction, and allowing free variation of all parameters, we calculate the geometric arrangements and energies of the lowest alpha-chain states. These configurations are then cranked to predict the maximum angular momenta and the excitation energies that they can sustain. We conclude that states similar to that in ²⁴Mg should also be accessible to experimental investigation in other nuclei.

References (9)

A.H. Wuosmaa et al.
Phys. Rev. Lett.
(1992)
W.D.M. Rae
Int. J. Mod. Phys.
(1988)
H. Crannell et al.
P.J. Nolan et al.
Ann. Rev. Nucl. Part. Sci.
(1988)
R.V.F. Janssens et al.
Ann. Rev. Nucl. Part. Sci.
(1991)

There are more references available in the full text version of this article.

Cited by (63)

Evidence for shape coexistence and superdeformation in 24Mg
2020, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
The E0 transition depopulating the first-excited $0^{+}$ state in ²⁴Mg has been observed for the first time, and the E0 transition strength determined by electron-positron pair and γ-ray spectroscopy measurements performed using the Super-e pair spectrometer. The E0 transition strength is $ρ^{2} \times 10^{3} = 380 (70)$ . A two-state mixing model implies a deformation of the first-excited $0^{+}$ state of $β_{2} \approx 1$ and a change in the mean-square charge radius of $Δ 〈 r^{2} 〉 \approx 1.9 {fm}^{2}$ , which suggests a significant shape change between the ground state and first-excited $0^{+}$ state in ²⁴Mg. The observed E0 strength gives direct evidence of shape coexistence and superdeformation in ²⁴Mg, bringing this nucleus into line with similar behaviour in nearby $N = Z$ nuclei. This result agrees with recent theoretical work on the cluster nature of ²⁴Mg and has potential ramifications for nuclear reactions of astrophysical importance.
Shape isomers of light nuclei from the stability and consistency of the SU(3) symmetry
2019, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Citation Excerpt :
The comparison with the results of the energy-minimum calculation is given in Table 1. The most systematic calculations have been carried out in Ref. [13] in terms of the Nilsson model, and in [14–16], in terms of the Bloch-Brink alpha-cluster model (for one, two, and three dimensional configurations). Therefore, we compare our results with those ones.
We investigate the stability and self-consistency of the SU(3) symmetry and quadrupole deformation in light nuclei in terms of the Nilsson model and quasi-dynamical symmetry. It turns out that SU(3) is a remarkably good symmetry for commensurable major axes, similarly to the finding of the simple harmonic oscillator interaction. The method serves as an alternative to the well-known energy-minimum calculation for the determination of the shape isomers. In case of the ¹⁶O, ²⁰Ne, and ²⁴Mg nuclei the results of the two different procedures are in good agreement with each other.
Nuclear clusters and nuclear molecules
2006, Physics Reports
Citation Excerpt :
The extension of these approaches to multi-centre nuclear molecules with valence particles, is a very appealing subject for future study. The mass 13 nuclei have been the subject of many shell–model calculations, e.g. [192,207,212,213] and references therein. Generally, normal (negative) parity states in 13C (and 13N) arise from various recouplings of the nine nucleons in the p-shell.
Clustering has long been known to be influential in the structure of ground and excited states of $N = Z$ nuclei. States close to the decay thresholds are of particular interest, as clustering becomes dominant. Recent studies of loosely bound light neutron-rich nuclei have focused attention on structures based on clusters and additional valence neutrons, which give rise to covalent molecular binding effects. These nuclear molecules appear only at the extremes of deformation, in the deformed shell model they are referred to as super- and hyper-deformed. The beryllium isotopes provide the first examples of such states in nuclear physics. Further nuclear molecules consisting of unequal cores and also with three centres can be considered. These arise in the isotopes of neon and carbon, respectively. Molecular states in intrinsically asymmetric configurations give rise to parity (inversion) doublets. Examples of recent experiments demonstrating the molecular structure of the rotational bands in beryllium isotopes are presented. Further experimental evidence for bands as parity doublets in nuclei with valence neutrons in molecular orbits is also analysed. Work on chain states (nuclear polymers) in the carbon isotopes is discussed. These are the first examples of hyper-deformed structures in nuclei with an axis ratio of 3:1. Future perspectives are outlined based on a threshold diagram for covalent nuclear molecules with clusters bound via neutrons in covalent molecular configurations.
Cluster states in 12C and 14C
2010, Modern Physics Letters A
Chain configurations in light nuclei
2007, International Journal of Modern Physics E
2+ Excitation of the 12C Hoyle state
2009, Physical Review C - Nuclear Physics

View all citing articles on Scopus

View full text

Article preview

Nuclear Physics A

Abstract

References (9)

Phys. Rev. Lett.

Int. J. Mod. Phys.

Ann. Rev. Nucl. Part. Sci.

Ann. Rev. Nucl. Part. Sci.

Cited by (63)

Evidence for shape coexistence and superdeformation in <sup>24</sup>Mg

Shape isomers of light nuclei from the stability and consistency of the SU(3) symmetry

Nuclear clusters and nuclear molecules

Cluster states in <sup>12</sup>C and <sup>14</sup>C

Chain configurations in light nuclei

2+ Excitation of the <sup>12</sup>C Hoyle state