Probing nucleon-nucleon correlations in heavy-ion transfer reactions

The γ-particle coincident measurements, performed by coupling of the PRISMA spectrometer to the large γ arrays (CLARA and AGATA), demonstrate a strong interplay between single-particle and collective degrees of freedom that is pertinent to the reaction dynamics. By using the unique PRISMA performance in terms of both resolution and efficiency, measurements at very low bombarding energies have been performed. Via transfer of nucleon pairs, valuable information on the component responsible for particle correlations has been derived

Partial Dynamical Symmetry and Anharmonicity in Gamma-Soft Nuclei

Partial dynamical symmetry is shown to be relevant for describing the anharmonicity of excited bands in $^{196}$Pt while retaining solvability and good SO(6) symmetry for the ground band.Comment: 4 pages, 1 figure, Proc. Int. Conf. on "Nuclear Structure and Dynamics", May 4-8, 2009, Dubrovnik, Croati

Energy functional based on natural orbitals and occupancies for static properties of nuclei

The possibility to use functionals of occupation numbers and natural orbitals for interacting fermions is discussed as an alternative to multi-reference energy density functional method. An illustration based on the two-level Lipkin model is discussed.Comment: Proceeding of the conference "Nuclear Structure and Dynamics", Dubrovnik, Croatia, 4-8 May, 200

Elastic α\alpha-transfer in the elastic scattering of 16^{\bf 16}O+12+^{\bf 12}C

The elastic scattering $^{16}$O$+^{12}$C angular distributions at $^{16}$O bombarding energies of 100.0, 115.9 and 124.0 MeV and their optical model description including the $\alpha$-particle exchange contribution calculated in the Coupled Reaction Channel approach are presented. The angular distributions show not only the usual diffraction pattern but also, at larger angles, intermediate structure of refractive origin on which finer oscillations are superimposed. The large angle features can be consistently described including explicitly the elastic $\alpha$-transfer process and using a refractive optical potential with a deep real part and a weakly absorptive imaginary part.Comment: 3 pages, 2 figures, accepted in Eur.Phys.J A (Short note

Non-empirical nuclear energy functionals, pairing gaps and odd-even mass differences

First, we briefly outline some aspects of the starting project to design non-empirical energy functionals based on low-momentum vacuum interactions and many-body perturbation theory. Second, we present results obtained within an approximation of such a scheme where the pairing part of the energy density functional is constructed at first order in the nuclear plus Coulomb two-body interaction. We discuss in detail the physics of the odd-even mass staggering and the necessity to compute actual odd-even mass differences to analyze it meaningfully.Comment: 8 pages, 1 figure, proceedings of the International Conference on Nuclear Structure and Dynamics, Dubrovnik, Croatia, May 4 - 8, 200

Orbiting-cluster model with combinatorial level density

The combinatorial nuclear level densities are used in the orbiting-cluster model calculations. Previous predictions of the model of resonance observability obtained for systems of mass A £ 56 with nuclear statistical-model (Bethe formula) level densities are confirmed. The present calculation correctly predicts resonances in barium isotopes, in accordance with recent experimental results, while the statistical model does not

Model kružećih grozdova s kombinatornom gustoćom stanja

The combinatorial nuclear level densities are used in the orbiting-cluster model calculations. Previous predictions of the model of resonance observability obtained for systems of mass A ≤ 56 with nuclear statistical-model (Bethe formula) level densities are confirmed. The present calculation correctly predicts resonances in barium isotopes, in accordance with recent experimental results, while the statistical model does not.Primijenili smo kombinatornu gustoću nuklearnih stanja u modelu orbitirajućih grozdova. Potvrdili smo ranija predviđanja vjerojatnosti opažanja rezonancija za sustave masa A ≤ 56 koja su bila dobivena rabeći gustoće stanja izračunate nuklearnim statističkim modelom (Betheova formula). Kombinatorni račun ispravno predviđa rezonancije u izotopima barija, u skladu s ishodima nedavnih mjerenja, dok statistički model daje loše rezultate

Slaba apsorpcija i rezonancije u lakim teškoionskim reakcijama izazvane jezgrom 14C koja nema α-podstrukturu

The observation of resonant structures attributed to nuclear molecular configurations in α-type systems involving the 12C and 16O nuclei is a clear signature of a weak and surface-transparent absorption in these light heavy-ion reactions at energies around and up to well above the Coulomb barrier. Such a weak absorption, i.e. nuclear-surface transparency, is also predicted in reactions induced by the 14C nucleus owing to the very special structure of low-lying states of this non-α-type nucleus. The experimental search for resonant structures in the 14C+14C, 14C+12C and 14C+16O reactions undertaken by the Strasbourg–Zagreb collaboration is described and discussed in the context of weak-absorption phenomena. Strong and correlated resonances have been observed in the three systems studied and particularly in those decay channels which are sensitive to the largest partial waves in the entrance channel. As the incident energy increases, weak and surface-transparent absorption gives rise to refractive effects, i.e to the nuclear rainbow. Indeed, nuclear rainbows have been observed recently in the same α-type 12C+12C, 12C+16O and 16O+16O systems in which prominent nuclear molecular resonances have been reported at lower energies. It is predicted that such refractive effects should also be observed in the 14C-induced reactions at energies above ∼ 5 MeV per nucleon.Opažanje rezonantnih struktura nuklearnih molekulskih konfiguracija u sustavima koji uključuju jezgre 12C i 16O, a koje imaju izrazitu grozdastu α-podstrukturu, jasan su znak slabe i površinski prozirne apsorpcije u lakim teškoionskim reakcijama na energijama oko i znatno iznad Coulombove barijere. Takva slaba apsorpcija, tj. prozirnost nuklearne površine, pređvida se također za reakcije izazvane jezgrom 14C zbog posebne strukture niskoležećih stanja te jezgre, iako nije jezgra α-tipa. U svjetlu pojava slabe apsorpcije, razmatramo eksperimentalno traženje rezonantnih struktura u reakcijama 14C+14C, 14C+12C i 14C+16O, koje smo poduzeli u okviru suradnje grupa iz Strasbourga i Zagreba. Opažene su jake i korelirane rezonancije u sva tri proučavana sustava, a napose u onim izlaznim reakcijskim kanalima koji su osjetljivi na doprinos najviših parcijalnih valova ulaznog kanala reakcije. Porastom upadne energije, slaba i površinski prozirna apsorpcija uzrokuje refraktivne pojave, odnosno nuklearnu dugu. Doista, nuklearna duga je nedavno opažena u sustavima α-tipa (12C+12C, 12C+16O i 16O+16O) za koje su na niskim energijama nađene izrazite nuklearne molekulske rezonancije. Pređvidamo da će se takve refraktivne pojave opaziti na energijama iznad oko 5 MeV po nukleonu i za reakcije izazvane jezgrom 14C

Slaba apsorpcija i rezonancije u lakim teškoionskim reakcijama izazvane jezgrom 14C koja nema α-podstrukturu

The observation of resonant structures attributed to nuclear molecular configurations in α-type systems involving the 12C and 16O nuclei is a clear signature of a weak and surface-transparent absorption in these light heavy-ion reactions at energies around and up to well above the Coulomb barrier. Such a weak absorption, i.e. nuclear-surface transparency, is also predicted in reactions induced by the 14C nucleus owing to the very special structure of low-lying states of this non-α-type nucleus. The experimental search for resonant structures in the 14C+14C, 14C+12C and 14C+16O reactions undertaken by the Strasbourg–Zagreb collaboration is described and discussed in the context of weak-absorption phenomena. Strong and correlated resonances have been observed in the three systems studied and particularly in those decay channels which are sensitive to the largest partial waves in the entrance channel. As the incident energy increases, weak and surface-transparent absorption gives rise to refractive effects, i.e to the nuclear rainbow. Indeed, nuclear rainbows have been observed recently in the same α-type 12C+12C, 12C+16O and 16O+16O systems in which prominent nuclear molecular resonances have been reported at lower energies. It is predicted that such refractive effects should also be observed in the 14C-induced reactions at energies above ∼ 5 MeV per nucleon.Opažanje rezonantnih struktura nuklearnih molekulskih konfiguracija u sustavima koji uključuju jezgre 12C i 16O, a koje imaju izrazitu grozdastu α-podstrukturu, jasan su znak slabe i površinski prozirne apsorpcije u lakim teškoionskim reakcijama na energijama oko i znatno iznad Coulombove barijere. Takva slaba apsorpcija, tj. prozirnost nuklearne površine, pređvida se također za reakcije izazvane jezgrom 14C zbog posebne strukture niskoležećih stanja te jezgre, iako nije jezgra α-tipa. U svjetlu pojava slabe apsorpcije, razmatramo eksperimentalno traženje rezonantnih struktura u reakcijama 14C+14C, 14C+12C i 14C+16O, koje smo poduzeli u okviru suradnje grupa iz Strasbourga i Zagreba. Opažene su jake i korelirane rezonancije u sva tri proučavana sustava, a napose u onim izlaznim reakcijskim kanalima koji su osjetljivi na doprinos najviših parcijalnih valova ulaznog kanala reakcije. Porastom upadne energije, slaba i površinski prozirna apsorpcija uzrokuje refraktivne pojave, odnosno nuklearnu dugu. Doista, nuklearna duga je nedavno opažena u sustavima α-tipa (12C+12C, 12C+16O i 16O+16O) za koje su na niskim energijama nađene izrazite nuklearne molekulske rezonancije. Pređvidamo da će se takve refraktivne pojave opaziti na energijama iznad oko 5 MeV po nukleonu i za reakcije izazvane jezgrom 14C

Refractive elastic scattering of carbon and oxygen nuclei: The mean field analysis and Airy structures

The experimental data on the $^{16}$O$+^{12}$C and $^{18}$O$+^{12}$C elastic scatterings and their optical model analysis are presented. Detailed and complete elastic angular distributions have been measured at the Strasbourg Vivitron accelerator at several energies covering the energy range between 5 and 10 MeV per nucleon. The elastic scattering angular distributions show the usual diffraction pattern and also, at larger angles, refractive effects in the form of nuclear rainbow and associated Airy structures. The optical model analysis unambiguously shows the evolution of the refractive scattering pattern. The observed structure, namely the Airy minima, can be consistently described by a nucleus-nucleus potential with a deep real part and a weakly absorptive imaginary part. The difference in absorption in the two systems is explained by an increased imaginary (mostly surface) part of the potential in the $^{18}$O$+^{12}$C system. The relation between the obtained potentials and those reported for the symmetrical $^{16}$O$+^{16}$O and $^{12}$C$+^{12}$C systems is drawn.Comment: 10 pages, 9 figures, Phys. rev. C in pres