Speaker
Marco Siciliano
(LNL)
Description
In the last years the robustness of the proton shell closure Z=50 has been studied when N=50 is approached: the excitation energy together with the reduced transition probabilities of the low-lying states provides a clear evidence of the shell evolution along the whole Sn isotopic chain.
However, the presence of low-lying isomers has limited the investigation of the electromagnetic properties of the first excited states; for this reason the neutron-deficient Sn isotopes have been studied only via Coulomb excitation measurements, employing radioactive beams.
The excitation energy of the first 2+ and 4+ states is well known and it is rather constant along the whole Sn isotopic chain. On the other hand, for the neutron-deficient Sn isotopes the B(E2;2+→0+) values suffer from large experimental uncertainties and the information on B(E2;4+→2+) is completely absent, which make the interpretation of the shell evolution controversial.
In order to obtain a precise estimation of the reduce transition probabilities in the region close to 100Sn, a multi-nucleon transfer reaction was used together with the Recoil Distance Doppler-Shift method as an alternative and complementary solution to the previously-performed Coulomb excitation measurements. This allowed to directly measure the lifetime of 2+ and 4+ states in 106,108Sn for the very first time and then to extract the B(E2) values of the low-lying states.
Large-scale shell-model calculations have been performed by taking into account the new experimental results. In particular, the comparison of the B(E2;4+→2+) values with the theoretical predictions has shed light on the nuclear structure in the vicinity of the proton drip line.
Selected session
Nuclear Structure and Dynamics
Primary authors
Alain Goasduff
(Università di Padova - INFN Sezione di Padova)
Jose' Javier Valiente Dobon
(LNL)
Marco Siciliano
(LNL)
