A determination of the number of alpha particles per second emitted by Thorium C of known gamma ray activity : A. G. Shenstone and H. Schlundt. (Phil. Mag., June, 1922.)
✍ Scribed by G.F.S.
- Publisher
- Elsevier Science
- Year
- 1922
- Tongue
- English
- Weight
- 89 KB
- Volume
- 194
- Category
- Article
- ISSN
- 0016-0032
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✦ Synopsis
Thorium C and its products produce, in the course of disintegration, alpha rays of ranges 8.6 centimetres and 5.0 centimetres in air, in the proportion of 65 to 35. At the same time they produce hard gamma radiation.
Radium C similarly emits hard gamma radiation and alpha particles of range 6.96 centimetres and 3.8 centimetres, the latter, however, appearing in negligible numbers." Since the number of alpha particles emitted per sec. per mg. is known for Radium C. it is possible to compute the corresponding number for Thorium C by making a comparison of the number of scintillations caused in a minute on a zinc sulphicle screen by the impact of the alpha particles from the two sources, the relative gamma ray activity being measured at the same time. The active deposit of thorium C was obtained by rotating a nickel disc for thirty minutes in a solution of radiothorium
To provide radium C, radium emanation was allowed to decay overnight in a glass tube.
The active matter deposited on the walls was dissolved in dilute hvdrochloric acid, and a nickel disc stirred the solution for a few minutes.
To avoid making large counts of scintillations a rotating wheel with a slot on its circumference was interposed between the active material and the zinc sulphide screen.
The alpha particles could reach the screen only through the slot.
The control measurements for gamma ray activity were made with an electroscope. " Thorium C should fall to half value in 6o.5 minutes and Radium C in 19.5 minutes. Actually we obtained decay curves giving periods of 60 to 61 minutes for thorium C and 19.5 to 20.2 for Radium C."
The mass of thorium C, which has the same activity as I mg. of radium and its products as measured by gamma rays that have in both cases traversed 3.3 mm. of lead, emits in one sec. 30,703,ooo alpha particles of 8.6 cm. range. G. F. S.