No abstract

The half‐life of 26Al has been redetermined because of suggestions of an error in the accepted value based on its use in calculating 21Ne production rates from cosmic rays in meteorites. Two solutions of 26Al were analyzed for the specific radioactivity and mass spectrometric determination of the 26Al concentration. The half‐life obtained for 26Al was 7.05×105 years ±3.4%. This is identical to the accepted value of 7.16×105 years and indicates that problems with the 21Ne production rate is not due to an erroneous half‐life.

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No abstract

We have measured (n, 2n) and (n, np+n, pn) cross sections for the radioactive nuclides "Y and Zr. The results are, for the (n, 2n) reaction on 'Y at 14. 19+0.04 MeV, 1140+50 mb; and at 14.8+0. 1 MeV, 1180+50 mb. The ' Y isomer ratios (m/total) ar'e 0.70+0.05 and 0.74+0.05, respectively.For "Zr at 14.8+0. 1 MeV, the (n, 2n) cross section is 467+23 mb, and the (n, np+n, pn) cross section is 253+25 mb. The ' Y isomer ratio for the latter reaction is 0.90+0.06.The results are compared to calculations which are based on a combined statistical-preequilibrium model. Half-lives for Zr, Zr, Y, and Y~a re presented. Branching ratios for the decay of Zr to Y ' were determined and the photon intensity of the 484.9-keV gamma ray from the decay of Y was measured.NUCLEAR REACTIONS Y(n, 2n)s7Y '~, E = 14.2, 14.8 MeV; Zr(n, 2n) Zr, E=14.8 MeV; Zr(n, 2n+ n, np) Ym, g E=14.8 MeV; measured g(E). Comparison with combined statistical and preequilibrium model. RADIOACTIVITY Y, Yg, Zr, Zr; measured half-life. Zr, measured branching decay. Yg, measured Iz.