<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mn>0</mml:mn><mml:mi>gs</mml:mi><mml:mo>+</mml:mo></mml:msubsup><mml:mo>→</mml:mo><mml:msubsup><mml:mn>2</mml:mn><mml:mn>1</mml:mn><mml:mo>+</mml:mo></mml:msubsup></mml:math>Transition Strengths in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi>Sn</mml:mi><mml:mprescripts/><mml:none/><mml:mn>106</mml:mn></mml:mmultiscripts></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mmultiscripts><mml:mi>Sn</mml:mi><mml:mprescripts/><mml:none/><mml:mn>108</mml:mn></mml:mmultiscripts></mml:math>
Аннотация
The reduced transition probabilities, $B(E2;{0}_{\mathrm{gs}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})$, have been measured in the radioactive isotopes $^{108,106}\mathrm{Sn}$ using subbarrier Coulomb excitation at the REX-ISOLDE facility at CERN. Deexcitation $\ensuremath{\gamma}$ rays were detected by the highly segmented MINIBALL Ge-detector array. The results, $B(E2;{0}_{\mathrm{gs}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})=0.222(19){e}^{2}{b}^{2}$ for $^{108}\mathrm{Sn}$ and $B(E2;{0}_{\mathrm{gs}}^{+}\ensuremath{\rightarrow}{2}_{1}^{+})=0.195(39){e}^{2}{b}^{2}$ for $^{106}\mathrm{Sn}$ were determined relative to a stable $^{58}\mathrm{Ni}$ target. The resulting $B(E2)$ values are $\ensuremath{\sim}30%$ larger than shell-model predictions and deviate from the generalized seniority model. This experimental result may point towards a weakening of the $N=Z=50$ shell closure.