2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/87640Symmetry adaptation techniques are applied to the determination of the intensity of two-photon transitions for transition ions in finite symmetry environments. We treat the case of intra-configurational transitions with some details and briefly report some results on inter-configurational transitions. In particular, for intra-configurational transitions, we describe a model which takes into account the following ingredients: symmetry, second- plus third- order mechanisms, S-, L- and J-mixings.11 pages, Tex file. Invited lecture at the "Second International School on Excited States of Transition Elements", Wroclaw-Karpacz, Poland, September 1991Atomic and Molecular ClustersCondensed MatterChemical Physicstext