Evidence for a spin-aligned neutron–proton paired phase from the level structure of 92Pd

Di Nitto, Antonio and La Rana, Giovanni and Moro, Renata and Vardaci, Emanuele (2011) Evidence for a spin-aligned neutron–proton paired phase from the level structure of 92Pd. [Pubblicazione su rivista scientifica]

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URL: http://www.nature.com/nature/journal/v469/n7328/full/nature09644.html


hell structure and magic numbers in atomic nuclei were generally explained by pioneering work that introduced a strong spin–orbit interaction to the nuclear shell model potential. However, knowledge of nuclear forces and the mechanisms governing the structure of nuclei, in particular far from stability, is still incomplete. In nuclei with equal neutron and proton numbers (N = Z), enhanced correlations arise between neutrons and protons (two distinct types of fermions) that occupy orbitals with the same quantum numbers. Such correlations have been predicted to favour an unusual type of nuclear superfluidity, termed isoscalar neutron–proton pairing, in addition to normal isovector pairing. Despite many experimental efforts, these predictions have not been confirmed. Here we report the experimental observation of excited states in the N = Z = 46 nucleus 92Pd. Gamma rays emitted following the 58Ni(36Ar,2n)92Pd fusion–evaporation reaction were identified using a combination of state-of-the-art high-resolution γ-ray, charged-particle and neutron detector systems. Our results reveal evidence for a spin-aligned, isoscalar neutron–proton coupling scheme, different from the previous prediction. We suggest that this coupling scheme replaces normal superfluidity (characterized by seniority coupling) in the ground and low-lying excited states of the heaviest N = Z nuclei. Such strong, isoscalar neutron–proton correlations would have a considerable impact on the nuclear level structure and possibly influence the dynamics of rapid proton capture in stellar nucleosynthesis.

Tipologia di documento:Pubblicazione su rivista scientifica
Altre informazioni:Preprint in fedOA: <http://www.fedoa.unina.it/7886>
Parole chiave:Experimental nuclear physics
Settori scientifico-disciplinari MIUR:Area 02 Scienze fisiche > FIS/04 FISICA NUCLEARE E SUBNUCLEARE
Stato del full text:Accessibilità ristretta
Data:06 Gennaio 2011
Numero di pagine:4
Intervallo di pagina:pp. 68-71
Dipartimento o Struttura:Scienze Fisiche
Stato dell'Eprint:Pubblicato
Numero identificativo:DOI:10.1038/nature09644
Titolo rivista/pubblicazione:Nature
Numero di sistema:7887
Depositato il:18 Febbraio 2011 13:25
Ultima modifica:13 Maggio 2011 11:41

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