DIRECT MASS MEASUREMENTS OF A=80 ISOBARS

Direct mass measurements of A=80 isobars were performed using the seco nd cyclotron of SARA (Systeme Accelerateur Rhone-Alpes) of the ISN (In stitut des Sciences Nucleaires) in Grenoble as a time-of-flight mass s pectrometer. Using the 300 MeV Ni-58 + Al-27 reaction, the isobars Rb- 80, Sr-80, Y-80, and Zr-80 (only one event!) were measured. For Y-80 w e found a mass value of 79.934320(180) u, corresponding to a decay ene rgy Q (Y-80, Sr-80) of (9120 +/- 170) keV. Comparing this value to the former experiments of Lister et al. and Della Negra et al. results in a difference of about 2.2 MeV. However, it does agree with the recomm ended value of Audi and Wapstra, which is derived from systematic tren ds. For Zr-80 the single event was identified with a probability of 0. 999975 and a mass value of 79.940400(1600) u could be deduced from our experiment.