The half-value period of uranium-Y

Abstract

Although uranium-Y was discovered by Antonoff in 1911, and confirmed by Soddy, no concordant values for its decay constant have been obtained owing, amongst other reasons, to the difficulty of obtaining a pure source of sufficient strength. Using a small source which they suspected of being contaminated with thorium, Hahn and Meitner obtained 25 ± 0·5 hours by measuring its decay in an electroscope fitted with a 10 μ aluminium foil base. Kirsch, using an electrometer, obtained the values 24·64 ± 0·27 hours, or 26 hours according to the shape of ionisation chamber, but attributed the longer value to the use of a field too weak to give saturation. On the other hand, using an α-ray electroscope, Guy and Russell obtained 27·8 hours as the mean of six concordant readings. Since the authors had available a strong source of U-Y of exceptional purity prepared for another purpose, they thought it advisable to redetermine this constant so as to decide between the very conflicting values hitherto obtained and, if possible, suggest an explanation for the discrepancies between the results of other workers.