Quadrupole correlations in $Sn$ isotopic chain: First direct lifetime measurement of ${}^{106,108}Sn$ low-lying states.

Siciliano M., Valiente-Dob'on J.J., Goasduff A., Bazzacco D., Alahari N., Benzoni G., Braunroth T., Cieplicka N., Crespi F.C.L., Clement E., de France G., Doncel M., Ert"urk S., Fransen C., Gadea A., Georgiev G., Goldkuhle A., Jakobsson U., Jaworski G., John P.R., Kuti I., Lemasson A., Lopez-Martens A., Li H., Lunardi S., Marchi T., Mengoni D., Michelagnoli C., Mijatovic T., M"uller-Gatermann C., Napoli D.R., Nyberg J., Palacz M., P'erez-Vidal R.M., Rejmund M., Saygi B., Sohler D., Szilner S., Testov D.
  Giovedì 14/09   16:00 - 19:00   Aula A208   I - Fisica nucleare e subnucleare
In the last years the robustness of the proton shell closure $Z=50$ has been studied when $N=50$ is approached: the reduced transition probabilities of the low-lying states provide a clear evidence of the shell evolution along the whole Sn isotopic chain. For the neutron-deficient Sn isotopes, the information on $B(E2; 4^{+}\rightarrow 2^{+})$ is completely absent and the $B(E2; 2^{+}\rightarrow 0^{+})$ values suffer from large experimental uncertainties, which make the interpretation of the shell evolution controversial. The quadrupole correlations of ${}^{106,108}Sn$ were studied by extracting the $B(E2)$ values of low-lying states: for the first time the lifetimes of $2^{+}$ and $4^{+}$ states were directly measured via the RDDS method using a plunger device.