On the basis of the definition of overlap polarizability of a chemical bond we propose that the overlap region in a molecule AB behaves as a localized plasma-like harmonic oscillator. Strong absorption and inelastic scattering by this oscillator are predicted in the far ultraviolet and near soft-X-ray spectral regions. Numerical estimates for representative diatomic molecules show a clear correlation with covalency, and suggest these absorption and inelastic scattering processes as a useful tool to characterize a chemical bond. (c) 2005 Elsevier B.V. All rights reserved.