The theory of the spectra of europium salts

Abstract

Abstract A theoretical analysis is given of the three 5D terms in the europium ion. The integrals Fk are discussed and the importance of F6 is emphasized. Values of F4/F2 and F6/F2 are calculated for a hydrogenic 4f eigenfunction, and evidence from the praseodymium and gadolinium ions suggests it is reasonable to use these values in the case of europium. A state in L, S, L2, S2 quantization is defined in terms of the determinantal product states of 4f one-electron states, and this enables the properties of the 5D terms to be found. By calculating the Coulomb energies of the three terms, it is shown that the 5D term observed spectroscopically is the lowest of the three. The relative positions of the levels 5D0, 5D1 and 5D2 that derive from this term are calculated for Russell-Saunders coupling, and a satisfactory fit is obtained with the observed spacings. In addition, the crystal fine structures of 7F1 and 5D1 are related to each other, and the agreement between experiment and theory is as good as can be expected.