Evidence for a highly deformed band in12C+16Obreakup of<

Abstract

The 16 O( 16 O, 12 C 16 O)␣ reaction has been studied at incident energies of 90 and 97 MeV. States in 28 Si are reconstructed over the excitation energy range 22-45 MeV, and the spins of six states, ranging from 9 Ϫ to 17 Ϫ , were obtained from angular correlation measurements. A comparison of these breakup states with scattering resonances indicates that some of the breakup states lie below the locus of the 12 Cϩ 16 O scattering resonances, and may belong to a highly deformed band with a rotational parameter of (42Ϯ5) keV and a bandhead energy of E x ϭ(26.3Ϯ0.9) MeV.

Inversion doublets of reflection-asymmetric clustering in Si28 and their isoscalar monopole and dipole transitions

“…These large overlaps mean that the equivalence of the cluster and shell model wave functions still remains despite the distortion effect. This result ensures that the degree of freedom of the 24 Mg + α cluster is embedded in the ground state of 28 Si. The negative-parity J π = 1 − state with the same 24 Mg + α (T) configuration [ Fig.…”

“…4(g), and has an excitation energy close to its positive-parity partner. We also obtained another 16 O + 12 C configuration having different orientation of the 12 C, which may correspond to the highly excited 16 O + 12 C cluster states or molecular resonances [23][24][25][26][27][28]. However, its energy is rather high and it is not discussed here.…”

“…If these bands really have clustering aspects, they must be accompanied by the negative-parity bands to constitute the inversion doublets, because of their reflection-asymmetric intrinsic configurations [35]. Therefore, the identification of the inversion doublet is rather essential to establish the clustering systematics in 28 Si, and in this study we extend our survey to the negative-party states.…”

“…[39,42], by assuming that the ground states is a pure SU(3) shell model state [43,44] and the excited states are ideal cluster states, it was analytically proved that the IS monopole and dipole transitions from the ground state to the excited cluster states are as strong as the single-particle estimates. However, in reality, the ground state of 28 Si deviates from a pure SU(3) shell model state because of the strong influence of the spin-orbit interaction. Furthermore, in the excited states, the cluster configurations are mixed with the mean-field configurations.…”

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Background: Various cluster states of astrophysical interest are expected to exist in the excited states of 28 Si. However, they have not been identified firmly, because of the experimental and theoretical difficulties.

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