Configuration-interaction many-body perturbation theory for La II electric-dipole transition probabilities

We report that accurate transition probabilities of La II ion are calculated using configuration-interaction many-body perturbation theory with 10 adjustable parameters, seven of which are evaluated from energies of the La III single-valence electron ion. Comparison is given for transitions probabilities and lifetimes with experiments and theories. Close agreement with experiment is observed for most transitions. The theoretical approach can be extended to other divalent atoms and ions with strong valence-core interactions and to more complex atoms. Laslty, the theory will be useful for opacity evaluation and astrophysical applications.