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Physical Review C 85 (2012) 034315
Isoscalar monopole excitations in $^{16}$O: $\alpha$-cluster states at low energy and mean-field-type states at higher energy
T. Yamada, Y. Funaki, T. Myo, H. Horiuchi, K. Ikeda, G. Roepke, P. Schuck1, 2, 3, A. Tohsaki
(2012)

Isoscalar monopole strength function in $^{16}$O up to $E_{x}\simeq40$ MeV is discussed. We found that the fine structures at the low energy region up to $E_{x} \simeq 16$ MeV in the experimental monopole strength function obtained by the $^{16}$O$(\alpha,\alpha^{\prime})$ reaction can be rather satisfactorily reproduced within the framework of the $4\alpha$ cluster model, while the gross three bump structures observed at the higher energy region ($16 \lesssim E_{x} \lesssim 40$ MeV) look likely to be approximately reconciled by the mean-field calculations such as RPA and QRPA. In this paper, it is emphasized that two different types of monopole excitations exist in $^{16}$O; one is the monopole excitation to cluster states which is dominant in the lower energy part ($E_{x} \lesssim 16$ MeV), and the other is the monopole excitation of the mean-field type such as one-particle one-hole ($1p1h$) which {is attributed} mainly to the higher energy part ($16 \lesssim E_{x} \lesssim 40$ MeV). It is found that this character of the monopole excitations originates from the fact that the ground state of $^{16}$O with the dominant doubly closed shell structure has a duality of the mean-field-type {as well as} $\alpha$-clustering {character}. This dual nature of the ground state seems to be a common feature in light nuclei.
1 :  IPNO - Institut de Physique Nucléaire d'Orsay
2 :  Grenoble 1 UJF - Université Joseph Fourier
3 :  LPMMC - Laboratoire de physique et modélisation des milieux condensés
Physique/Physique Nucléaire Expérimentale

Physique/Physique Nucléaire Théorique
Lien vers le texte intégral : 
http://fr.arXiv.org/abs/1110.6509