Precision Mass Measurements beyond $^{132}$Sn: Anomalous behaviour of   odd-even staggering of binding energies
  Atomic masses of the neutron-rich isotopes $^{121-128}$Cd, $^{129,131}$In, $^{130-135}$Sn, $^{131-136}$Sb, and $^{132-140}$Te have been measured with high precision (10 ppb) using the Penning trap mass spectrometer JYFLTRAP. Among these, the masses of four r-process nuclei $^{135}$Sn, $^{136}$Sb, and $^{139,140}$Te were measured for the first time. The data reveals a strong $N$=82 shell gap at $Z$=50 but indicates the importance of correlations for $Z>50$. An empirical neutron pairing gap expressed as the odd-even staggering of isotopic masses shows a strong quenching across $N$=82 for Sn, with the $Z$-dependence that is unexplainable by the current theoretical models. 
J. Hakala, J. Dobaczewski, D. Gorelov, T. Eronen, A. Jokinen, A.   Kankainen, V. S. Kolhinen, M. Kortelainen, I. D. Moore, H...
nucl-ex