4f collapse in rare earth ions produces an enormous level density due to the occurrence of near-degeneracies of 4f/5p and 4f/5s binding energies. As a result, there is a complete breakdown of the single-particle approximation and the level and line spectra satisfy many of the distributions associated with random matrix theory. Similar behaviour has been previously reported in spectra associated with wavefunction contraction effects or atoms containing open 4f subshells; here the effects of combining both phenomena are explored. In particular it is shown that the adjacent level separations satisfy a Wigner distribution, while transitions between them obey the Porter-Thomas distribution. Detailed Hartree-Fock calculations show that there is a strong correlation between line strength and transition energy. This correlation is pursued and parametrized for the particular case of 4f → 5d, 5p → 5d and 5s → 5p transitions in Sm IX within the unresolved transition array model.
|Number of pages||13|
|Journal||Journal of Physics B: Atomic, Molecular and Optical Physics|
|Publication status||Published - 28 Jan 2002|