Accurate masses of neutron-deficient nuclides close to Z=82

Mass measurements with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN are extended to nonsurface ionizable species using newly developed ion-beam bunching devices. Masses of Hg179-197, Pb-196,Pb-198, Bi-197, Po-198 and At-203 were determined with an accuracy of 1 x 10(-7) corresponding to deltam approximate to 20 keV. Applying a resolving power of up to 3.7 x 10(6) ground and isomeric states of Hg-185,Hg-187,Hg-191,Hg-193,Hg-197 were separated. First experimental values for the isomeric excitation energy of Hg-187,Hg-191 are obtained. A least-squares adjustment has been performed and theoretical approaches are discussed to model the observed fine structure in the binding energy. (C) 2001 Elsevier Science B.V. All rights reserved.