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The total b 2 decay energies of 14 nuclides in the vicinity of 132 Sn have been measured using high resolution spectroscopic methods. The present results derived for the atomic masses in this region are significantly more precise than the previously accepted values, and differ significantly from these in some cases. The precision of the new mass values surpasses that expected from the systems currently proposed for direct mass measurements of nuclei far from stability. The present results resolve a recently observed and highly puzzling discrepancy between the experimental mass values in the 132 Sn region and theoretical systematics. [S0031-9007(99)08609-3] PACS numbers: 21.10. Dr, 21.60.Cs, 23.20.Lv, 27.60. + j The mass data in the vicinity of doubly closed shells (DCS) for nucleons give highly valuable structure information. This has a particular significance for the far-fromstability regions where new phenomena may arise due to low binding energies. Precise binding energies, derived from the atomic masses, are also of critical importance for the modeling of the astrophysical r process, especially in the regions bordering the doubly closed shell nuclei of 78 Ni and 132 Sn. Consequently, it was of particular concern that the accepted masses of the neutron rich N 82 isotones in the vicinity of 132 Sn have been recently questioned [1] on the grounds of a "serious inconsistency" with predictions based on a shell model reduction technique. The authors compare a mass "window" W calculated using a specific combination of the N 82 ground state masses, to the value of W extracted via a simple formula involving the experimental excited state energies in 134 Te and 135 I. A significant difference of almost 500 keV has been noted [1] between W 23570 keV from level spectroscopy and W 23080 ͑150͒ keV from the N 82 masses [2]. Since such a comparison gives an agreement to within a few keV for the N 126 isotopes at 208 Pb, the authors conclude [1] that the N 82 mass values could be inaccurate by considerably more than the estimated errors. However, this particular conclusion was later challenged in the first theoretical work [3] employing a realistic effective interaction for shell model calculations of the N 82 isotones. The authors of Ref.[3] claim that some approximations used in the derivation of W, as well as configuration admixtures in the states involved, can have a significant influence on the values obtained from the shell model reduction method. Other theoretical arguments, presented later in the present paper, suggest that the reduction method cannot in all cases yield a precise agreement with the experimental mass data, but nevertheless it should be applicable to the N 82 and N 126 nuclides of interest in the comparisons of Zhang et al. [1]. Quite clearly, there is an obvious need for an experimental clarification of the mass data in close vicinity to 132 Sn for the dual purpose of understanding the inconsistency between experimental data and a seemingly well-founded empirical systematics, and to establish a very...

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