New neutron deficient isotope 85Nb

New isotopes 83Nb and 85Nb are identified by analyzing the decay process of low-lying levels of 83Zr and 85Zr determined from in-beam data. Protons and alpha-particles are mainly released from neutron deficient nuclei away from stable beta-rays. When charged particles are released, it is difficult to identify residues from measurements of gamma-ray sum-energy and multiplicity. A detector to measure the multiplicity of charged particles is constructed and applied to identification of particles. Signals representing the number of particles and alpha-particles are detected together with gamma-ray energy and TAC signals. Spectra gated by one proton and one alpha-particle in the 60Ni + 28Si are observed. From these spectra, the number of protons and alpha-particles in each gamma-ray channel can be investigated to determine the z-number of the gamma-ray release nuclides. In addition, neutron-gamma coincidence measurement is made to determine the gamma-rays released by 85Zr. Isotope decay measurement is compared with calculation of cross sections made according to the statistical theory. As a result, it is concluded that the 50 keV gamma-ray found in this measurement is attributed to the decay of 85Nb. Positron spectrum is measured in coincidence with 50.1 keV gamma-ray following the decay of 85Nb and the β+ end point energy of 85Nb is determined. It is concluded that the half-life of 85Nb is 20.9 ± 7 sec. and QEC is 6.3 ± 0.3 MeV. (Nogami, K.)