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Accueil du site > Publications récentes > Neutron 2p and 1f spin-orbit splittings in 40Ca, 36S, and 34Si N = 20 isotones : Tensor-induced and pure spin-orbit effects

Neutron 2p and 1f spin-orbit splittings in 40Ca, 36S, and 34Si N = 20 isotones : Tensor-induced and pure spin-orbit effects

M. Grasso

Neutron 2p and 1f spin-orbit splittings were recently measured in the isotones 37S and 35Si by (d,p) transfer reactions. Values were reported by using the major fragments of the states. An important reduction of the p splitting was observed, from 37S to 35Si, associated with a strong modification of the spin-orbit potential in the central region of the nucleus 35Si. We analyze 2p and 1f neutron spin-orbit splittings in the N = 20 isotones 40Ca, 36S, and 34Si. We employ several Skyrme and Gogny interactions to reliably isolate pure spin-orbit and tensor-induced contributions, within the mean-field approximation. We use interactions (i) without the tensor force, (ii) with the tensor force and with tensor parameters adjusted on top of existing parametrizations, nd (iii) with the tensor force and with tensor and spin-orbit parameters adjusted simultaneously on top of existing parametrizations. We predict in cases (ii) and (iii) a non-negligible reduction of both p and f splittings, associated with neutron-proton tensor effects, from 40Ca to 36S. The two splittings are further decreased for the three types of interactions, going from 36S to 34Si. This reduction is produced by the spin-orbit force and is not affected by tensor-induced contributions. For both reductions, from 40Ca to 36S and from 36S to 34Si, we predict in all cases that the modification is more pronounced for p than for f splittings. The measurement of the centroids for neutron 2p and 1f states in the nuclei 36S and 34Si would be interesting to validate this prediction experimentally. We show the importance of using interactions of type (iii), because they provide p and f splittings in the nucleus 40Ca which are in agreement with the corresponding experimental values.

Voir en ligne : Phys. Rev. C 92, 054316 (2015)


 

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