Is it ensure, insure, or assure?
enrichment of one isotope relative to another in a chemical or physical process. Two isotopes of an element are different in weight but not in gross chemical properties, which are determined by the number of electrons. However, subtle chemical effects do result from the difference in mass of isotopes. Isotopes of an element may have slightly different equilibrium constants for a particular chemical reaction, so that slightly different amounts of reaction products are made from reactants containing different isotopes. This leads to isotopic fractionation, the extent of which can be expressed by a fractionation factor, alpha (alpha), also known as a separation factor, or enrichment factor. This factor is the ratio of the concentrations of the two isotopes in one compound divided by the ratio in the other compound. If Nl and Nh stand for the relative abundances of the light and heavy isotopes, respectively, in the original compound and if nl and nh are the corresponding abundances in the new compound, then alpha = (Nl/Nh)/(nl/nh). The fractionation factor is the factor by which the abundance ratio of two isotopes will change during a chemical reaction or a physical process.