Direct mass measurements of A=80 isobars

Direct mass measurements of A=80 isobars were performed using the second cyclotron of SARA (Systeme Accelerateur Rhone-Alpes) of the ISN (Institut des Sciences Nucleaires) in Grenoble as a time-of-flight mass spectrometer. Using the 300 MeV 58Ni +27Al reaction, the isobars 80Rb, 80Sr, 80Y, and 80Zr (only one event!) were measured. For 80Y we found a mass value of 79.934320(180) u, corresponding to a decay energy Q (80Y →80Sr) 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 recommended value of Audi and Wapstra, which is derived from systematic trends. For 80Zr 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.