New approach to the theory of intermediate valence

The single $f$-state impurity problem involved in a local-intermediate-valence model has been solved by using time-dependent multiple-scattering theory. The density operator of the impurity state has been obtained in terms of $S$-matrix elements. It has been found that the present theory leads to a new type of hybridization which remains finite even when the crystal has inversion symmetry. General features of the method and its importance from an experimental viewpoint have been discussed.