Mobilities of mixtures of ion isotopes in gas mixtures

It is shown how the mobility of a mixture of isotopes of the same ion species in a gas mixture can be obtained directly from mobility data of a single isotope of the ion and one isotope of each neutral species, for any gas temperature and ratio of the electrostatic field strength to the gas number density. This combination of the “aliasing” procedure for ion isotopes, Blanc’s Law for gas mixtures at low fields, and the extended Blanc’s Law at intermediate and high fields is tested by comparing values calculated from the mobilities of ⁷⁹Br^? in ²⁰Ne with those determined both experimentally and ab initio for various mixtures. It is so accurate that it obviates the necessity in future work of making measurements or calculations for more than one isotope of each ion and each neutral.