Author index to volume 31

The problem of multiphoton absorption by an atom is formulated in terms of Brückner-Goldstone many-body perturbation theory with emphasis on the two-photon ionization of lithium. The series of terms in the perturbation expansion is summed up by using multiple basis sets. The result is represented by means of three primary diagrams. A more transparent interpretation of the ionization process is presented. Expressions for transition probabilities are obtained both for the linearly and circularly polarized photons. It is shown that the explicit introduction of the many-particle interaction does not change the angular distribution of the ejected electrons as compared to earlier calculations. The numerical results obtained for the transition probabilities in the limit of no correlation are found to agree with those of Mizuno.