PHYSICAL REVIEW LETTERS, cilt.102, sa.12, 2009 (SCI-Expanded)
Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the Hg-208 (Z=80, N=128) isotope. The mass excess value of ME=-13 265(31) keV has been obtained, which has been used to determine the proton-neutron interaction strength in Pb-210, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the N=126 neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons.