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Rare earths and copper systems were studied using X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS). The use of monochromased synchrotron radiation and improved energy resolution for RIXS made possible to obtain valuable information on the electronic structure in 4f, 5f and 3d systems. Experimental results for rare-earths (Ho, Gd, Cm,U, Np, Pu) were analyzed by atomic multiplet theory based on the Hartree-Fock calculations.

The inelastic scattering structures in RIXS spectra at 5d edge of actinides found to be sensitive to actinide oxidation states in different systems. Comparison of experimental and calculated Cm 5d RIXS spectra gave direct information about valency of the 248-curium isotope in oxide.

Scientific understanding of processes that control chemical changes of radioactive species from spent fuel is improved by studying interactions of actinide ions (U, Np, Pu) with corroded iron surfaces. RIXS measurements at the actinide 5d edge indicate the reduction of U(VI), Np (V) and Pu (VI) to U(IV), Np(IV) and Pu (IV) by presence of iron ions.

This thesis is also addressed to the study of changes in the electronic structure of copper films during interaction with synthetic groundwater solutions. The surface modifications induced by chemical reactions of oxidized 100Å Cu films with Cl⁻, SO₄²⁻ and HCO₃^– ions in aqueous solutions with various concentrations were studied in-situ using XAS. It was shown that the pH value, the concentration of Cl⁻ ion and presence of HCO₃^– ion in the solutions strongly affect the speed of the corrosion reaction. The Cu 2p RIXS was used to distinguish between the species present on the copper surface while in contact with groundwater solution.