A MASS SPECTROMETER AND THE MEASUREMENT OF ISOTOPE EXCHANGE FACTORS

Abstract

A 180 degree direction focusing mass spectrometer for isotope abundance measurements is described. In operation, the instrument has a resolution of one mass unit in 100, which is the resolution expected from the dimensions of the slits and the radius of curvature of the ion path.The precision of the instrument is sufficiently good to make possible the direct measurement of equilibrium constants for many isotopic reactions. Several reactions previously used to separate the nitrogen and the sulphur isotopes have been investigated. The equilibrium constants for the two reactions[Formula: see text]were found to be about 60% higher than those previously reported from fractionation column experiments. However, the low values previously reported can be accounted for on the basis of Cohen's theory of packed columns.