On the Isotopic Ratio in Oxygen

Abstract

A new mass-spectrometer has been constructed along lines previously described in which the defects that appeared in the first apparatus are eliminated. The electrostatic analyzer has been slightly altered to take full advantage of its focussing properties for which a formula is given. Because of the faintness of the scattered background, very weak peaks can be measured precisely. Oxygen, prepared by the decomposition of Pb${\mathrm{O}}_2$, has been analyzed and the ratio of the amount of ${\mathrm{O}}^{16}$ to ${\mathrm{O}}^{18}$ found to be 503 ±10. It is suggested that the discrepancy between this and previous values may be due to the method of preparation of the oxygen sample.