New Radioactivity 43-min Yttrium-84

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Abstract
A New 43±2-min yttrium radioactivity has been observed in the natural strontium target irradiated with 57-MeV protons. It is assigned to Y 84 by measuring the excitation function. The 3.7-hr activity previously assigned to Y 84 is identified to Y 85 . Gamma transitions of 0.453 MeV (10%), 0.590-MeV (15%),0.795-MeV (100%, E2), 0.982-MeV (100%, E2), 1.041-MeV (50%, E2 or M1), 1.27-MeV (9%), and 1.47-MeV (6%) are observed in the scintillation and internal conversion spectra of Y 84 . The positron spectrum taken with a beta-ray spectrometer gives maximum energies of 3.50±0.10-MeV and 2.90±0.15-MeV. Gamma-Gamma and positron-gamma coincidence measurements are carried out. A tentative decay scheme is proposed. It involves the following energy levels in Sr 84 : 0.982 or 0.795 MeV (2+), 1.777-MeV (4+), 2.367-MeV, 2.818-MeV, etc. The spin and parity of Y 84 are tentatively assigned as 5-.

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