Isotopic Constitution of Lead from Hyperfine Structure

Abstract

The relative abundance of the isotopes of lead was determined from intensity measurements of the hyperfine structure components of the lead spark line $\lambda 5372$. With eleven calibrated wire screens a single order of the Fabry-Perot interference pattern was photographed with the same exposure time for each screen. The following results from densitometer measurements were obtained for the percentage abundance of the isotopes of ordinary lead: 51.5, 26.3, 21.4 and 0.8 for ${\mathrm{Pb}}^{208}$, ${\mathrm{Pb}}^{206}$, ${\mathrm{Pb}}^{207}$, and ${\mathrm{Pb}}^{204}$, respectively. For integral masses of the isotopes the mean mass number is ${207.22}_8$. Assuming a packing factor of +1, this number when converted to the chemical atomic weight scale becomes 207.20.