Fine-Structure Constant Connects Electronic Polarizability and Geometric van-der-Waals Radius of Atoms

Abstract

The fine-structure constant (FSC) measures the coupling strength between photons and charged particles and is more strongly associated with quantum electrodynamics than with atomic and molecular physics. Here we present an elementary derivation that accurately predicts the electronic polarizability of atoms A from their geometric van-der-Waals (vdW) radius RvdW and the FSC α through the compact formula A = (4πϵ0/a04) × α4/3RvdW7, where ϵ0 is the permittivity of free space and a0 is the Bohr radius. The validity of this formula is empirically confirmed by estimating the value of α from nonrelativistic quantum calculations of atomic polarizabilities and atomic vdW radii obtained from both theory and experiment. Our heuristic derivation based on empirical data extends the influence of FSC from quantum electrodynamics and specific materials properties such as the visual transparency of graphene to atomic electronic properties throughout the periodic table of elements.