Enhanced Coulomb repulsion (electron) screening around light element nuclei is achieved by way of utilizing target structures (e.g., nanoparticles) that undergo plasmon oscillation when subjected to electromagnetic (EM) radiation, whereby transient high density electron clouds are produced in localized regions of the target structures during each plasmon oscillation cycle. Each target structure includes an integral body composed of an electrically conductive material that contains light element atoms (e.g., metal hydrides, metal deuterides or metal tritides). The integral body is also configured (i.e., shaped/sized) to undergo plasmon oscillations in response to the applied EM radiation such that the transient high density electron clouds are formed during each plasmon oscillation cycle, whereby brief but significantly elevated charge density variations are generated around light element (e.g., deuterium) atoms located in the localized regions, thereby enhancing Coulomb repulsion screening to enhance nuclear fusion reaction rates. Various target structure compositions and configurations are disclosed.