Correlation Between Fermi-Energy, Chemical Shifts, and Surface Plasmon Resonance in Cu and Zn Compounds under X-ray Illumination

This study represents an integrated theoretical framework that correlates copper (Cu) and zinc (Zn) compounds with variation in Fermi energy, chemical shifts, and surface plasmon resonance (SPR) under X-ray illumination. A simplified but conscientious model was developed to determine chemical shifts in X-ray K-absorption spectra based on Fermi energy differences between metals and their compound states. The model incorporates electron concentration, plasmon energy, and effective charge to predict more clearly the sign as well as the amount of chemical shift without depending on empirical adaptation. Experimental X-ray absorption data closely match the expected chemical shifts (2.7-6.0 eV for Cu compounds and 2.4-4.7 eV for Zn compounds), confirming the model's reliability. A correlation between Fermi energy and effective charge confirms that electron redistribution of compounds governs spectral edge shifts under X-ray illumination. Furthermore, the conceptual link between Fermi-level modulation and SPR behavior illustrates that variations in conduction electron density are influenced by X-ray illumination. This correlation reveals a consistent theoretical explanation for photo-induced plasmonic phenomena in Cu, Zn, and their compounds based materials. Overall, the suggested model enhances perception of the Fermi energy dependence of chemical shifts and extends its applicability to plasmonic materials. The current study offers a frontier analysis tool that will be used for the electronic and optical properties of transition-metal compounds.