Lifetime measurements in ${}^{105}Sn$: The puzzle of B(E2) and B(M1) strengths in Sn isotopes.

Pasqualato G. , Gottardo A., Goasduff A., Mengoni D., Valiente-Dobon J.J., de Angelis G., Bakes S.D., Bayram T., Bazzacco D., Benzoni G., Brugnara D., Cicerchia M., Colovic P., Cortés M.L., Gadea A., Galtarossa F., Gorska M., Gozzelino A., Gregor E., Hubbard N., Illana A., Lenzi S.M., Mantovani G., Marchi T., Menegazzo R., Montaner-Pizá A., Napoli D.R., Recchia F., Siciliano M., Testov D., Zanon I.

I - Fisica nucleare e subnucleare
Aula Palazzo dell'Emiciclo - Sala Ipogea - Mercoledì 25 h 10:00 - 13:00
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Nowadays, a great amount of experimental effort is devoted to the study of the shell closures far from stability. A prominent nucleus in this context is the heaviest doubly magic and self-conjugated ${}^{100}Sn$. While it is still unreachable for in-beam spectroscopy of its excited states, the decay-spectroscopy provided indirect indication that the shell closure is present. To test the robustness of the proton shell closure approaching $N=50$ the spectroscopy of the Sn isotopic chain therefore becomes useful. The study of the reduced transition probabilities via fusion-evaporation reaction is hampered by the presence of low-lying isomers in even-even Sn isotopes. In this context, the lifetimes of ${}^{105}Sn$ have been investigated through the reaction ${}^{50}Cr({}^{58}Ni,2pn)$. The experiment was performed at Legnaro National Laboratories using the Compton-suppressed HPGe -ray spectrometer GALILEO in coincidence with the charged particle Si detector EUCLIDES and four $LaBr_3$ scintillators at $90^{\circ}$ with respect to the beam direction. This setup allows one to perform $\gamma - \gamma$ and $\gamma$-particles coincidences to select the channel of interest. The presence of the plunger device enables one to measure the lifetime of the excited states thanks to the Recoil Distance Doppler Shift technique.

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