A New Determination of the Disintegration Constant of Uranium by the Method of Countingα-Particles

Abstract

Alpha-particles emitted by a known amount of pure ${\mathrm{U}}_3$ ${\mathrm{O}}_8$ in the form of thin films were restricted in their passage into an ionization vessel by cylindrical channels of a grid placed over the material. The method of counting $\alpha$-particles alone was that of Greinacher. All $\alpha$-particles entering the ionization chamber automatically registered on a mechanical counter, for which an elaborate electrical and mechanical arrangement of apparatus was used. Over 100,000 counts were made from two specimens differing in surface density in the ratio of nearly 5 to 1. The ${\lambda }_{\mathrm{UI}}$ obtained is ${1.53}_2$ ${\mathrm{}\left(10\right)\mathrm{}}^{-10\mathrm{}}$ ${\mathrm{yr}}^{-1\mathrm{}}$ or $T={4.52}_4{\mathrm{}\left(10\right)\mathrm{}}^9$ yr, a value consistent with Gleditsch's ${\lambda }_{\mathrm{Ra}}=4.11\mathrm{}{\mathrm{}\left(10\right)\mathrm{}}^{-4\mathrm{}}$ ${\mathrm{yr}}^{-1\mathrm{}}$, Boltwood's radium to uranium ratio of 7.40${\mathrm{}\left(10\right)\mathrm{}}^{-7\mathrm{}}$ and branching ratio between 0.96 and 0.97.