Abstract
It was shown that the evolution of the $B(E2;{2}_{1}^{+}\ensuremath{\rightarrow}{0}_{1}^{+})$ values in $N$ = 80 isotones from Te to Nd is affected by the underlying subshell structure. This manifests itself in the observation of the local suppression of the $B(E2)$ value at $Z=58$ with respect to the neighboring nuclei $^{136}\mathrm{Ba}$ and $^{140}\mathrm{Nd}$. To investigate this shell sensitivity toward the $Z=64$ subshell gap, the $B(E2;{2}_{1}^{+}\ensuremath{\rightarrow}{0}_{1}^{+})$ value of the unstable nucleus $^{142}\mathrm{Sm}$ was measured utilizing the projectile Coulomb excitation technique. The radioactive ion beam (RIB) experiment was performed at the REX-ISOLDE facility at CERN. The $B(E2)$ value of $32\phantom{\rule{0.16em}{0ex}}(4)\phantom{\rule{0.16em}{0ex}}\mathrm{W}.\mathrm{u}.$ reflects the impact of the $\ensuremath{\pi}(1{g}_{7/2}\phantom{\rule{0.16em}{0ex}}2{d}_{5/2})$ subshell closure at $Z=64$ with respect to a linear scaling of collectivity with valence proton number.
Highlights
How collectivity arises from the dynamics of the nuclear many-body system is a not fully solved problem in nuclear structure physics
Even-even nuclei and their This behavior is generic between major shells indicating that low-energy quadrupole collectivity is a valence shell effect
It can be expected that the evolution of collective properties in between major shell closures should analogously be modulated by the underlying subshell structure
Summary
How collectivity arises from the dynamics of the nuclear many-body system is a not fully solved problem in nuclear structure physics. The key approach to this problem is based on understanding the relations between the collective correlations and the specific single-particle structures This is illustrated by the anticorrelation between the level energies B(E2; 2+1 of →. It can be expected that the evolution of collective properties in between major shell closures should analogously be modulated by the underlying subshell structure. Such modulations are usually smeared out by the pairing interaction. An example for collective states affected by the underlying subshell structure was identified in the isovector quadrupole-collective valence-shell excitations, so-called mixed-symmetry states [3], in the N = 80 isotones [4]. In the present article we report on the result of a projectile Coulombexcitation experiment determining the B(E2; 2+1 → 0+1 ) value of 142Sm
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