A simple semiempirical model for the static polarizability of ions

Abstract

A concise analytical model for the static dipole polarizability of ionized atoms and molecules is created for the first time. As input, it requires, alongside the polarizability of neutral counterpart of a given ion, only the charge and elemental composition. This physically motivated semiempirical model is based on a number of established regularities in polarizability of charged monatomic and polyatomic compounds. In order to adjust it, the results of quantum chemistry calculations and gas-phase measurements available for a broad range of ionized multielectron species are employed. To counteract the appreciable bias in the literature data toward polarizability of monoatomic ions, for some molecular ions of general concern the results of the authors’ own density functional theory calculations are additionally invoked. A total of 541 data points are used to optimize the model. It is demonstrated that the model we suggested has reasonable (given the substantial uncertainties of the reference data) accuracy in predicting the static isotropic polarizability of arbitrarily charged ions of any size and atomic composition. The resulting polarizability estimates are found to achieve a coefficient of determination of 0.93 for the assembled data set. The created analytic tool is universally applicable and might be advantageous for some applications where there is an urgent need for rapid low-cost evaluation of the static gas-phase polarizability of ionized atoms and molecules. This is especially relevant to constructing the complex models of nonequilibrium chemical kinetics aimed at precisely describing the observable refractive index (dielectric permittivity) of plasma flows. The data sets that support the findings of this study are openly available in Science Data Bank at https://doi.org/10.57760/sciencedb.07526.