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The High Frequency Spectra of Lead Isotopes

1920; American Institute of Physics; Volume: 16; Issue: 4 Linguagem: Inglês

10.1103/physrev.16.327

1536-6065

C. D. Cooksey, D. Cooksey,

Radioactive Decay and Measurement Techniques

Least Detectable Difference in Wave-length Dependent on Distance between Lines and Length of Reflected Ray.---Reasons are given for confining the work to a comparison of the $L{\ensuremath{\alpha}}_{1}$ lines of ordinary and uranio-lead. The least detectable difference in wave-length between two lines on the same plate is directly proportional to the least detectable distance between their axes and inversely to the length of the reflected ray between the crystal and plate. However, the nature of the $L{\ensuremath{\alpha}}_{1}$ line of lead is such as to make it more important to reduce as much as possible the least detectable distance between the lines, than it is to increase the length of the reflected ray.Limit of Accuracy. Special Method of Suspending and Displacing Plateholder.---The spectrometer is described in detail in the preceding article. A special method of suspending the plateholder and giving it a known displacement is described, by which it is possible to fix the limit of accuracy directly. An X-ray bulb of the gas type was used with a specially designed anode which could be rotated so as to bring different parts of its face under the action of the cathode stream. The two kinds of lead were placed on different parts of the same anode. The uranio-lead was from a primary uraninite from India.Upper Half of Line from One Lead and Lower Half from Other Photographed on Same Plate.---The ${\ensuremath{\alpha}}_{1}$ line of one kind of lead was photographed on the upper half of the plate, and the same line from the other lead on the lower half, immediately below it. Full lines for reference were sometimes photographed near the half lines for measurement purposes. The limit of accuracy was found by giving the plate a known displacement between the taking of one half and the other, of a line from the same kind of lead.$L{\ensuremath{\alpha}}_{1}$ Lines from Ordinary and Uranio-lead Do Not Differ in Wave-length by as much as 0.005 Per Cent.---It is found that a displacement between two half lines of ${(10)}^{\ensuremath{-}3}$ mm. can be readily detected and that the wave-lengths of the $L{\ensuremath{\alpha}}_{1}$ lines of the two kinds of lead can not differ by as much as 0.6 \ifmmode\times\else\texttimes\fi{} ${(10)}^{\ensuremath{-}4}$ \AA{}., or 0.005 per cent.