Radioactivité naturelle du lutétium, du rhénium et de l'osmium

Abstract
Some studies of the decay of 176Lu have been made by Dixon, Mc Nair and Curran with the help of the large proportional tube spectrometer and scintillation spectrometers. Sources down to 0.1 mg/cm2 in thickness were spread over the large cathode and the shape of the β continuum, endpoint 425 ± 25 keV, together with the internal conversion peaks observed. The conversion coefficients were evaluated. The γ ray spectrum and the γ-γ coincidence spectra showed that γ rays of energies 310, 190 and 89 keV were emitted in cascade. They arose in transitions from levels of spin and parity 6+, 4+ and 2+. The decay scheme fitted accurately the Bohr-Mottelson predictions. The ground state of 116Lu seemed to be a 10+state. The maximum branching by K-capture was 3 per 100. The half-life was 4.56 × 1010g for 176Lu. Studies by Dixon and Glover on 184Re and 184Os failed to reveal β-activity or capture and minimum half-lives of 1016 years were deduced. Apparent evidence of capture in 184Os was found to be due to a specific " background" effect and this effect could explain weak capture activities, for instance that tentatively assigned to 113In. Work on 22Na by Moljk, with extremely thin sources in the proportional tube, is important in the general problem of observing very soft Auger electrons released in capture decay. The position spectrum was found to be closely allowed in shape down to 15 keV or less. The capture intensity, as examined by searching for Auger electrons, was not more than 3 per 100. Thèse is still some uncertainty about thé release of extremely soft electrons from such sources. Experiments of Moljk and Curran on 14C and 35S as gaseous sources (CH4 and CS2) showed that both spectra were allowed in shape to better than 1 per 100 down to an energy of about 2 keV, New techniques for such examination were described.