X-ray photoelectron study of actinide (Th, U, Pu, Am) nitrates

In this work an X-ray photoelectron spectroscopy study of nitrates Th(NO3)4·4H2O, UO2(NO3)2·nH2O, Pu(NO3)4·nH2O, and Am(NO3)2·nH2O was done in the binding energy range from 0 to 1000 eV in order to draw a correlation of the fine spectral structure parameters with the actinide ions oxidation states, close environment structure, and chemical bond nature. The linearity of the dependence of the An5fn line intensity on the number n5f of the An5f electrons was proven to remain up to the Am3+ ion with the electron configuration {Rn}5f6. The spectral structure in the binding energy range from 0 to ∼ 15 eV was associated with the formation of the outer valence molecular orbitals due to the interaction of the An6d-, 7s, 5f - O2p electrons, and the fine spectral structure in the binding energy range from ∼15 to ∼50 eV - with the formation of the inner valence molecular orbitals due to the interaction of the An6p - O2s electrons from the filled neighboring atomic orbitals of actinide and oxygen in the studied compounds. The fine structure of the core level electron spectra in the binding energy range from ∼50 to 1000 eV was shown to correlate with the actinide ion oxidation state. (author)