Theβ-spectrum of MsTh1 (Ra228) has been measured in a proportional counter in 2π — and in 4π-geometry. Comparison of these measurements shows that there are no conversion electrons. Theβ-decay of MsTh 1 therefore leads in all cases to the ground level of MsTh2. The Kurie plot is straight from 15 keV up to the upper energy limit ofE0=55±3 keV (logft=5·6). The result has been checked by a search for photons emitted by the MsTh1. Noγ-rays and no X-rays have been found. The measurements had to be made with a relatively large amount of natural Ra226 in the sources. — The results do not agree with those ofLecoin, Perey, Teillac andRiou, who proposed a complex decay sheme for MsTh1.
Unable to display preview. Download preview PDF.