"Clusters in light Nuclei"
Christian Beck, IPHC Strsabourg and Universite de Strasbourg
(id #167)
Seminar: NoPoster: No
Invited talk: Yes
A great deal of research work has been performed in the field of alpha clustering since the pioneering discovery, by Bromley and his collaborators half a century ago, of molecular resonances in the excitation functions for 12C+12C scattering [1]. Our knowledge of this field of nuclear molecular physics has increased considerably [2] and nuclear clustering remains one of the most fruitful domains of nuclear physics [3-4], facing some of the greatest challenges and opportunities in the years ahead.
The question whether quasimolecular resonances always represent true cluster states in the compound systems, or whether they may also simply reflect scattering states in the ion-ion potential is still unresolved [1-3,5]. Inmany cases, these resonant structures have been associated with strongly-deformed shapes and with clustering phenomena, predicted from the Nilsson-Strutinsky approach, the cranked -cluster model, or other mean-field calculations (see for instance Ref.[6] and references therein). Of particular interest is the relationship between superdeformation (SD) and nuclear molecules, since nuclear shapes with major-to-minor axis ratios of 2:1 have the typical ellipsoidal elongation (with quadrupole deformation parameter 2 0.6) for light nuclei. Furthermore, the structure of possible octupole-unstable 3:1 nuclear shapes (with 2 1.0) - hyperdeformation (HD) - for actinide nuclei has also been widely discussed in terms of clustering phenomena. Typical examples of the possible link between quasimolecular bands and extremely deformed (SD/HD) shapes have been widely discussed in the literature for N=Z nuclei such as 28Si [7], 32S [8], 36Ar [9-11], 40Ca [12] and 48Cr [13].
Large quadrupole deformations and -clustering in light N = Z nuclei are known to be general phenomena at low excitation energy. For high angular momenta and higher excitation energies, very elongated shapes are expected to occur in a-like nuclei for ACN = 20-60. In fact, highly deformed shapes and SD rotational bands have been recently discovered in several such N = Z nuclei, in particular, 36Ar using -ray spectroscopy techniques [14]. Extremely deformed rotational bands in 36Ar are observed as quasimolecular bands in both 12C+24Mg and 16O+20Ne reactions [9-11], and their related ternary clusterizations are also predicted theoretically [11]. The most recent results obatiend on ternary fission in light N=Z reactions [9,15] will also be discussed in terms of predicted hyperdeformed structure of cluster states.
[1] K.A. Erb and D.A. Bromley, Treatise on Heavy Ion Science, Vol. 3, p. 201, Ed. Plenum, New York (1985).
[2] W. Greiner, J. Y. Park, andW. Scheid, Nuclear Molecules, Ed. World Scientific (1995).
[3] M. Freer, Rep. Prog. Phys. 70, 2149 (2007).
[4] W. von Oertzen, M. Freer, and Y. Kanada-En’yo, Phys. Rep. 432, 43 (2006).
[5] C. Beck, Y. Abe, N. Aissaoui, B. Djerroud, and F. Haas, Phys. Rev. C 49, 2618 (1994).
[6] C. Beck et al., Phys. Rev. C 80, 034604 (2009) a
The question whether quasimolecular resonances always represent true cluster states in the compound systems, or whether they may also simply reflect scattering states in the ion-ion potential is still unresolved [1-3,5]. Inmany cases, these resonant structures have been associated with strongly-deformed shapes and with clustering phenomena, predicted from the Nilsson-Strutinsky approach, the cranked -cluster model, or other mean-field calculations (see for instance Ref.[6] and references therein). Of particular interest is the relationship between superdeformation (SD) and nuclear molecules, since nuclear shapes with major-to-minor axis ratios of 2:1 have the typical ellipsoidal elongation (with quadrupole deformation parameter 2 0.6) for light nuclei. Furthermore, the structure of possible octupole-unstable 3:1 nuclear shapes (with 2 1.0) - hyperdeformation (HD) - for actinide nuclei has also been widely discussed in terms of clustering phenomena. Typical examples of the possible link between quasimolecular bands and extremely deformed (SD/HD) shapes have been widely discussed in the literature for N=Z nuclei such as 28Si [7], 32S [8], 36Ar [9-11], 40Ca [12] and 48Cr [13].
Large quadrupole deformations and -clustering in light N = Z nuclei are known to be general phenomena at low excitation energy. For high angular momenta and higher excitation energies, very elongated shapes are expected to occur in a-like nuclei for ACN = 20-60. In fact, highly deformed shapes and SD rotational bands have been recently discovered in several such N = Z nuclei, in particular, 36Ar using -ray spectroscopy techniques [14]. Extremely deformed rotational bands in 36Ar are observed as quasimolecular bands in both 12C+24Mg and 16O+20Ne reactions [9-11], and their related ternary clusterizations are also predicted theoretically [11]. The most recent results obatiend on ternary fission in light N=Z reactions [9,15] will also be discussed in terms of predicted hyperdeformed structure of cluster states.
[1] K.A. Erb and D.A. Bromley, Treatise on Heavy Ion Science, Vol. 3, p. 201, Ed. Plenum, New York (1985).
[2] W. Greiner, J. Y. Park, andW. Scheid, Nuclear Molecules, Ed. World Scientific (1995).
[3] M. Freer, Rep. Prog. Phys. 70, 2149 (2007).
[4] W. von Oertzen, M. Freer, and Y. Kanada-En’yo, Phys. Rep. 432, 43 (2006).
[5] C. Beck, Y. Abe, N. Aissaoui, B. Djerroud, and F. Haas, Phys. Rev. C 49, 2618 (1994).
[6] C. Beck et al., Phys. Rev. C 80, 034604 (2009) a
