1203.0958 (J. Hakala et al.)

Precision Mass Measurements beyond $^{132}$Sn: Anomalous behaviour of
odd-even staggering of binding energies    [PDF]

J. Hakala, J. Dobaczewski, D. Gorelov, T. Eronen, A. Jokinen, A. Kankainen, V. S. Kolhinen, M. Kortelainen, I. D. Moore, H. Penttilä, S. Rinta-Antila, J. Rissanen, A. Saastamoinen, V. Sonnenschein, J. Äystö

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.

View original: http://arxiv.org/abs/1203.0958