Electronic structure and spectra of actinyl ions

Actinyl complexes are shown, on the basis of known theoretical and experimental results, to be weak-field complexes in 4/7 of the 5f orbital space, the other 3/7 of this space being strongly affected by bonding to the yl oxygens. The interactions present in these complexes are placed in order of size so that a coupling scheme (Lambda -S), including the choice of quantum numbers of varying quality, can be specified. Electronic spectra in the near-infrared and visible regions are discussed in general terms, including different choices of both the lower and upper orbitals (or spin-orbitals) involved in the excitations. For the isolated ions, all transitions in this region are forbidden by electric-dipole selection rules, but the interactions with equatorial ligands can make such transitions allowed.