Discovery of Tantalum, Rhenium, Osmium, and Iridium Isotopes

Currently, thirty-eight tantalum, thirty-eight rhenium, thirty-nine osmium, and thirty-eight iridium, isotopes have been observed and the discovery of these isotopes is discussed here. For each isotope a brief synopsis of the first refereed publication, including the production and identification method, is presented.Comment: To be published in At. Data Nucl. Data Table

Investigation of isomer ratios in the reactions (γ, \u3ci\u3en\u3c/i\u3e) and (\u3ci\u3en\u3c/i\u3e, 2\u3ci\u3en\u3c/i\u3e) on nuclei \u3csup\u3e76\u3c/sup\u3eGe and \u3csup\u3e82\u3c/sup\u3eSe

The method of the induced activity measured the isomeric yield ratios and cross-sections ratios of reactions (γ, n) and (n, 2n) on nuclei 76Ge and 82Se. Samples of natural have been irradiated in the bremsstrahlung beam of the betatron SB-50 of National University of Uzbekistan in the energy range of 10-35 MeV with energy step of 1 MeV. For 14 MeV neutron irradiation, we used the NG-150 neutron generator of Institute of Nuclear Physics. The gamma spectra reactions products were measured with a spectroscopic system consisting of HPGe detector CANBERRA with energy resolution of 1.8 keV at 1332 keV gamma ray of 60Co, amplifier 2022 and multichannel analyzer 8192 connected to computer for data processing. The filling of the isomeric and ground levels was identified according to their γ lines. Values η = Ym/(Ym + Yg) at Eγ max = 30 MeV for the reaction (γ, n) on nuclei 76Ge and 82Se are respectively: 0.55±0.02 and 0.36±0.01 (Ym/Yg = 0.56±0.02). In the range 26-35 MeV the isomeric yield ratios η of the reaction (γ, n) on 76Ge and 82Se are obtained at first. The isomeric cross-section ratios σm/σg was determined in the case of the reaction (n, 2n). In order to obtain the absolute values of the cross sections for the ground state and for the isomeric state, use was made of methods based comparing the yields of the reaction under study and the monitoring reaction. The reaction 27Al(n, α) 24Na (T1/2 = 15 h, Eγ = 1368 keV), whose cross section γm was 121.57±0.57 mb at En= 14.1 MeV, was taken for a monitoring reaction

New isotopes /sup 178/Ir, /sup 180/Ir, /sup 181/Ir

These isotopes, the half-lives of which are respectively 0.5+or-0.3, 1.5+or-0.1, 5.0+or-0.3 minutes, are identified. The data obtained are basically in agreement with similar data published by the ISOLDE group (CERN, 1970). (18 refs)