Quadrupole collectivity in neutron-deficient Sn nuclei:104Sn and the role of proton excitations

V. M. Bader, A. Gade, D. Weisshaar, B. A. Brown, T. Baugher, D. Bazin, J. S. Berryman, A. Ekström, M. Hjorth-Jensen, S. R. Stroberg, W. B. Walters, K. Wimmer (+1 others)
2013 Physical Review C  
We report on the experimental study of quadrupole collectivity in the neutron-deficient nucleus \nuc{104}{Sn} using intermediate-energy Coulomb excitation. The $B(E2; 0^+_1 \rightarrow 2^+_1)$ value for the excitation of the first $2^+$ state in \nuc{104}{Sn} has been measured to be $0.180(37)~e^2$b$^2$ relative to the well-known $B(E2)$ value of \nuc{102}{Cd}. This result disagrees by more than one sigma with a recently published measurement \cite{Gua13}. Our result indicates that the most
more » ... s that the most modern many-body calculations remain unable to describe the enhanced collectivity below mid-shell in Sn approaching $N=Z=50$. We attribute the enhanced collectivity to proton particle-hole configurations beyond the necessarily limited shell-model spaces and suggest the asymmetry of the $B(E2)$-value trend around mid-shell to originate from enhanced proton excitations across $Z=50$ as $N=Z$ is approached.
doi:10.1103/physrevc.88.051301 fatcat:t2dyfq62tnfmnib35436dnwcoi