STUDY OF THE BETA+/EC DECAY OF THE NEUTRON DEFICIENT NUCLEI SR-76, SR-78 AND Y-79

The beta+/EC decay of the neutron deficient nuclei 76,78Sr and 79Y was studied employing mass separated molecular beams of SrF+ and YF2+ from the ISOLDE mass separator. The halflives of 76,78Sr and 79Y were measured as tl/2 = 8.9(3)s, 159(8)s and 14.4(15)s, respectively, and decay schemes were established for 76Sr and 79Y. In the 78Sr decay 10 new gamma-ray transitions were identified. The investigation of the beta+/EC decay of the neutron deficient isotopes of Sr and Y following spallation reactions and successive mass separation is hampered by the fact, that the Rb isotopes are ionized much more efficiently in a typical surface ionization source. This led in the past to the unusual situation that the short lived N almost-equal-to Z isotopes of Sr and Y were first identified and studied in-beam, whereas their ground state properties and the beta+/EC decay could not be investigated. Chemical separation in addition to mass separation is needed to produce pure sources of the most neutron deficient Sr and Y isotopes.