[en] Two recent observational studies of the [Fe II] λ12567/λ16435 line ratio by Smith and Hartigan and Rodriguez-Ardila et al. have suggested that the available theoretical A-values could be incorrect to 10%-40%. We have carried out an extensive configuration interaction calculation of [Fe II] lines to investigate this claim, as well as the variability in observed line ratios for λ8617/λ9052 and λ8892/λ9227 of Dennefeld. For these transitions, we are generally in good agreement with the results of Nussbaumer and Storey, less so with those of Quinet et al. In comparison, the ratios derived from observations appear either to be less secure, or other factors influence those results.

[en] The nonrelativistic dipole-length, -velocity and -acceleration absorption oscillator strengths for the 1s²2s-1s²np(3≤n≤9) transitions of the lithium isoelectronic sequence up to Z=10 are calculated by using the energies and the multiconfiguration interaction wave functions obtained from a full core plus correlation (FCPC) method. In most cases, the agreement between the f-values from the length and velocity formulae is up to forth or fifth digit. Combining these discrete oscillator strengths with the single channel quantum defect theory (QDT), the discrete oscillator strengths for the transitions from the 1s^22s state to highly excited levels (n≥10) and the oscillator strength densities corresponding to the bound-free transitions are obtained. (orig.)

[en] A formal and numerical comparison of two of the most promising types of multiconfiguration wavefunction optimization methods, the super-CI methods and the exponential operator methods, is performed. The super-CI methods display superior convergence properties when the initial wavefunction is far from correct while the exponential operator methods possess superior convergence characteristics when the initial wavefunction is close to correct. The formal comparison of these approaches suggests hybrid methods which have some of the advantages of both methods. Unitary group methods have been successfully employed in the implementation of a general and efficient multiconfiguration wavefunction optimization program using these exponential operator and hybrid methods and a discussion of this implementation is included

No abstract available

[en] Theoretical and computational aspects in correlated methods are discussed such as: configuration interaction, many body perturbation theory and coupled-cluster. (A.C.A.S.)

No abstract available

[en] We extend the Angular Correlated Configuration Interaction method to two confined correlated electrons confined by harmonic potentials.

[en] Published in summary form only

[en] The configuration interaction method has been widely used to calculate electronic excitations in nanostructures, but it suffers from a slow rate of convergence with the number of configurations in the basis set and from the inability to select a priori the most important configurations. The optimized configuration interaction method presented here removes the limitations of the conventional approach by identifying at the outset the configurations that are most relevant for describing electronic excitations. We show that the 'best' configurations are remarkably different from the configurations that one would expect on the basis of the single-particle energy ladder, and that a small, optimized set of configurations predicts excitation energies with accuracy comparable to that for much larger, non-optimized sets of configurations. This approach opens the way to a new generation of configuration interaction methods where the configurations are pre-selected using heuristic search methods

[en] The problem of long-range configuration interaction between ionic and covalent states is considered. The existing methods for calculation of this interaction are discussed. An asymptotically exact expression for the long-range configuration interaction at the crossing point of diabatic ionic and covalent potentials is derived. Using this expression the adiabatic energy splitting at the crossing point for H*+H, M+H, and M+O systems (M = alkali atom) is calculated. The results are compared with those obtained by LCAO and variational calculations