SCHOTTKY MASS MEASUREMENTS OF COOLED PROTON-RICH NUCLEI AT THE GSI EXPERIMENTAL STORAGE-RING

High-precision mass measurements of proton-rich isotopes in the range of 60 less than or equal to Z less than or equal to 84 were performed using the novel technique of Schottky spectrometry. Projectile fragmen ts produced by Bi-209 ions at 930A MeV were separated with the magneti c spectrometer FRS and stored and cooled in the experimental storage r ing (ESR). A typical mass resolving power of 350 000 and a precision o f 100 keV were achieved in the region A approximate to 200. Masses of members of alpha chains linked by precise Q(alpha) values but not yet connected to the known masses were determined. In this way it is concl uded that Fr-201 and At-197 are proton unbound.