Search for proton radioactivity in65As,69Br and77Y

Abstract

A search for proton radioactivity in 65As, 69Br and 77y, produced as residues of fusion reactions, was carried out at the Orsay Tandem accelerator. The residues were collected at the image point of the spectrometer Soleno and implanted into the gaseous medium of an ionization chamber which was also used to detect the radioactivity protons. No such protons have been observed in the energy range of 250-600 keV and in the half-life interval of 10 gs-100 ms, within a production cross section sensitivity of l gb.

Half-life measurements forGa61,Ge

“…Since various mass predictions [8] disagree on whether these nuclei are bound, experiments are necessary to determine their primary decay modes. A number of experiments have attempted to observe ground-state proton decay for As and Br [6,9,10], but with no positive results. These null results did not require that the nuclei P decay since no direct evidence for the production of the nuclei was provided.…”

New Isotopes fromK78rFragmentation and the Ending Point of the Astrophysical Rapid-Proton-Capture Process

“…These facts triggered searches for the ground-state proton decay of 6sAs and 69Br [5,6]. However, both papers reported on the nonobservation of protons in the expected energy range.…”

“…However, both papers reported on the nonobservation of protons in the expected energy range. Therefore they concluded that either the decay of these nuclei is dominated by P decay or the groundstate proton-decay half-life is shorter than the respective experimental limits of 100 [6] and 10 p, s [5]. Mohar impinging on a nickel target, an experiment recently performed at the A1200 separator of MSU.…”

Beta-delayed proton decay ofSe65

“…Searches for the ground state proton emis- [7,8,9], with an upper limit for the proton decay branch to be less than 0.5% [7]. However, recent experiments [4] have, in fact, confirmed the existence of As.…”