Abstract
A value of 3.7 × yr (± 10%) for the half-life of was determined by a direct method involving measurement of both the specific activity [(dis/min )/(μg Mn)] and the isotope ratio (/). The specific activities were determined by neutron activation, and the / isotopic ratios by mass spectrometry. A surface-ionization method was applied using a rhenium single filament with the sample mounted in a silica-gel layer. This technique gave a stable and enhanced ion beam of . One source of was an electroplated Cr target bombarded by 15-MeV particles in a cyclotron. The other source of was the Mn fractions extracted from iron meteorites by carrier-free processes. Activities of 10 dis/min and 2000 dis/min were obtained with about 2 μg of from the Cr target. The isotopic ratio / was 750. Activities of about 1 (dis/min )/(μg Mn) and isotopic ratios / of 3000-4000 were obtained from the iron-meteorite extracts.
- Received 30 April 1971
DOI:https://doi.org/10.1103/PhysRevC.4.1182
©1971 American Physical Society