The previously pioneered Isochronous Mass Spectrometry (IMS) has been extended by an additional precise magnetic-rigidity determination to enable accurate large-scale measurements of stored short-lived relativistic nuclei with the FRS-ESR facility at 382 MeV/u. With this novel experimental tool the mass resolving power and accuracy have been improved by a factor of about 3. The recorded broad-band revolution time spectrum corresponds to the mass-over-charge range of about 6%. A mass resolving power of 200 000 (FWHM) and a typical accuracy of 120 keV have been achieved almost over the entire spectrum. The masses of 35 neutron-rich nuclides have been directly measured in the element range from aluminum to barium. The Masses of 8 nuclides (As-85,As-86, Se-89, Ag-123, Te-138, I-140,I-141, Xe-143) have been measured for the first time. The results are compared with previous experimental data and theoretical predictions. The evolution of the N = 50 shell closure towards doubly-magic Ni-78 is discussed. (c) 2008 Elsevier B.V. All rights reserved.