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Article
Title	Restoration of the N=82 Shell Gap from Direct Mass Measurements of $^{132,134}$Sn
Author(s)	Dworschak, M (GSI, Darmstadt, Germany) ; Audi, G (CNRS, Univ. Paris Sud, Orsay, France) ; Blaum, K (GSI, Darmstadt, Germany ; Johannes Gutenberg-Univ., Mainz, Germany ; Max Planck Inst. for Nuclear Physics, Heidelberg, Germany) ; Delahaye, P (CERN) ; George, S (GSI, Darmstadt, Germany ; Johannes Gutenberg-Univ., Mainz, Germany) ; Hager, U (Univ. Jyväskylä, Jyväskylä, Finland) ; Herfurth, F (GSI, Darmstadt, Germany) ; Herlert, A (CERN) ; Kellerbauer, A G (Max Planck Inst. for Nuclear Physics, Heidelberg, Germany) ; Kluge, H J (GSI, Darmstadt, Germany ; Ruprecht-Karls-Univ., Heidelberg, Germany) ; Lunney, D (CNRS, Univ. Paris Sud, Orsay, France) ; Schweikhard, L (Ernst-Moritz-Arndt-Univ., Greifswald, Germany) ; Yazidjian, C (GSI, Darmstadt, Germany)
Publication	2008
In:	Phys. Rev. Lett. 100 (2008) 072501
DOI	10.1103/PhysRevLett.100.072501
Subject category	Nuclear Physics - Experiment
Accelerator/Facility, Experiment	CERN ISOLDE ; IS413
Abstract	A high-precision direct Penning trap mass measurement has revealed a 0.5-MeV deviation of the binding energy of $^{134}$Sn from the currently accepted value. The corrected mass assignment of this neutron-rich nuclide restores the neutron-shell gap at N=82, previously considered to be a case of “shell quenching.” In fact, the new shell gap value for the short-lived $^{132}$Sn is larger than that of the doubly-magic $^{48}$Ca which is stable. The N=82 shell gap has considerable impact on fission recycling during the $r$ process. More generally, the new finding has important consequences for microscopic mean-field theories which systematically deviate from the measured binding energies of closed-shell nuclides.