High-accuracy mass determination of unstable cesium and barium isotopes

Direct mass measurements of short-lived Cs and Ba isotopes have been perfor med with the tandem Penning trap mass spectrometer ISOLTRAP installed at th e on-line isotope separator ISOLDE at CERN. Typically, a mass resolving pow er of 600 000 and an accuracy of delta m approximate to 13 keV have been ob tained. The masses of Ba-123,Ba-124,Ba-126 and Cs-122m were measured for th e first time. A least-squares adjustment has been performed and the experim ental masses are compared with theoretical ones, particularly in the frame of a macroscopic-microscopic model. (C) 1999 Elsevier Science B.V. All righ ts reserved.