Extended parametrization scheme of f-spectra

The standard one particle parametrization scheme of f-spectra which is based on the second-order Judd-Ofelt theory of electric dipole f⟷f transitions in lanthanides is extended by new terms. The extended scheme, although still one particle in origin, is defined in terms of double tensor operators that act within the spin-orbital space. In addition to the discussion of the physical mechanisms, which give rise to the new parameters, the results of numerical calculations performed for the Eu3+ ion in acetate crystal are presented as an illustration. In the discussion of the accuracy of the reproduction of the intensities of observed transitions, the problem of the theoretical description of the hypersensitive transitions is also addressed.