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1. |
NOTE ON THE PERMANENCE OF STANDARDS OF LENGTH |
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Canadian Journal of Research,
Volume 17a,
Issue 5,
1939,
Page 71-76
R. H. Field,
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摘要:
A few reasons are presented for believing that the fundamental standards for the Metre and the Yard, and also the legal Dominion Standards of length, are not changing appreciably. On the other hand, measurements of a number of laboratory nickel-iron rules show progressive shortening which is still taking place, through periods up to 20 years.
ISSN:1923-4287
DOI:10.1139/cjr39a-006
出版商:NRC Research Press
年代:1939
数据来源: NRC
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2. |
UNE ÉLECTRODE ARGENT–CARBONATE D'ARGENT OBTENUE PAR ÉLECTROLYSE |
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Canadian Journal of Research,
Volume 17a,
Issue 5,
1939,
Page 77-81
Pierre Demers,
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摘要:
not available
ISSN:1923-4287
DOI:10.1139/cjr39a-007
出版商:NRC Research Press
年代:1939
数据来源: NRC
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3. |
THE β- AND γ-RAYS OF ACTINIUM B AND ACTINIUM C″ |
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Canadian Journal of Research,
Volume 17a,
Issue 5,
1939,
Page 82-102
B. W. Sargent,
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PDF (1204KB)
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摘要:
The absorption method of finding the end-point of a β-ray spectrum has been made more precise and free of errors that are due to straggling and the γ-ray background. The absorption curves of the β-rays of radium E and uranium X2were taken as standard, since, from experiments with the magnetic spectrograph, their end-points are known to be 1.15 and 2.32 Mev respectively. The extrapolated ranges of these fastest β-rays are, from experiments with homogeneous beams, 0.51 and 1.12 gm. per cm.2of aluminium. In general the extrapolated rangeRcan be expressed in terms of the energyEin Mev by the equation:forE > 0.6 Mev. It is shown that the final portions of the absorption curves of the β-rays from radium E and uranium X2have the same shape when plotted againstm/R, wheremis the mass in gm. per cm.2of absorber andRis the range of the fastest β-rays in the spectrum. The range and end-point of another β-spectrum can be found by fitting its absorption curve to the standard one.The absorption curve of the β-rays of actinium B was obtained separately from that of actinium C″ for the first time. Growth curves were plotted from measurements of the β-activity of the active deposit obtained by exposing aluminium foils to filtered actinon for a few minutes. The β-activity was measured through thickness of aluminium up to 0.32 gm. per cm.2From the initial portions of the growth curves and from the absorption curve of the β-rays of actinium (B + C) in equilibrium, separate absorption curves were plotted which indicated ranges of 0.64 and 0.68 gm. per cm.2of aluminium for the β-rays of actinium B and actinium C″ respectively. The corresponding end-points are 1.39 and 1.47 Mev.There is some evidence that the β-spectrum of actinium B consists of two primary components, namely, a strong one having an end-point at 1.39 Mev and a weak one having an end-point at about 0.5 Mev. The difference between the two end-points is approximately equal to the energy (0.83 Mev) of a γ-ray emitted in the transformation actinium B.C. The ratio of the numbers of β-particles in the two partial spectra is approximately 1:7. This gives an excitation probability of 0.12 for the 0.83 Mev level of the actinium C nucleus, which is of the same order of magnitude as that obtained from the intensities of the γ-rays.
ISSN:1923-4287
DOI:10.1139/cjr39a-008
出版商:NRC Research Press
年代:1939
数据来源: NRC
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