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- Title
Oxygen-16 spectrum from tetrahedral vibrations and their rotational excitations.
- Authors
Halcrow, C. J.; King, C.; Manton, N. S.
- Abstract
A reinterpretation of the complete energy spectrum of the Oxygen-16 nucleus up to 20 MeV, and partly beyond, is proposed. The underlying intrinsic shape of the nucleus is tetrahedral, as in the naive alpha-particle model and other cluster models, and A-, E- and F-vibrational phonons are included. The A- and F-phonons are treated in the harmonic approximation, but the E-vibrations are extended into a two-dimensional E-manifold of D 2 -symmetric, four-alpha-particle configurations, following earlier works. This allows for the underlying tetrahedral configuration to tunnel through a square configuration into the dual tetrahedron, with the associated breaking of parity doubling. The frequency of an E-phonon is lower than in other models, and the first-excited 0 + state at 6.05 MeV is modeled as a state with two E-phonons; this allows a good fit of the lowest 2 + and 2 − states as excitations with one E-phonon. Rotational excitations of the vibrational states are analyzed as in the classic works of Dennison, Robson and others, with centrifugal corrections to the rotational energy included. States with F-phonons require Coriolis corrections, and the Coriolis parameter ζ is chosen positive to ensure the right splitting of the 3 + and 3 − states near 11 MeV. Altogether, about 80 states with isospin zero are predicted below 20 MeV, and these match rather well the more than 60 experimentally tabulated states. Several high-spin states are predicted, up to spin 9 and energy 30 MeV, and these match some of the observed high-spin, natural-parity states in this energy range. The model proposed here is mainly phenomenological but it receives some input from analysis of skyrmions with baryon number 16.
- Subjects
NUCLEAR cluster model; BARYON number; ALPHA rays; SKYRME model; SKYRMIONS; PHONONS
- Publication
International Journal of Modern Physics E: Nuclear Physics, 2019, Vol 28, Issue 4, pN.PAG
- ISSN
0218-3013
- Publication type
Article
- DOI
10.1142/S0218301319500265