J an 2 00 6 Configuration Interaction calculations of positron binding to Be ( 3 P o )
The Configuration Interaction method is applied to investigate the possibility of positron binding to the metastable beryllium (1s22s2p 3Po) state. The largest calculation obtained an estimated energy that was unstable by 0.00014 Hartree with respect to the Ps + Be+(2s) lowest dissociation channel. It is likely that positron binding to parent states with non-zero angular momentum is inhibited by centrifugal barriers.
Convergence of partial-wave expansions for energies, scattering amplitudes and positron annihilation rates
We use many-body theory to find the asymptotic behaviour of second-order correlation corrections to the energies and positron annihilation rates in many-electron systems with respect to the angular momenta l of the single-particle orbitals included. The energy corrections decrease as 1/(l + ½)4, in agreement with the result of Schwartz, whereas the positron annihilation rate has a slower 1/(l + ½)2 convergence rate. We illustrate these results by numerical calculations of the energies of Ne and Kr and by examining results from extensive configuration-interaction calculations of PsH binding and annihilation.
Relativistic oscillator strengths and excitation energies for the ns2 1S0-nsnp 3P1, 1P1 transitions. II. Cadmium isoelectronic sequence
For pt.I see ibid., vol.18, no.8, p.1533 (1985). Relativistic excitation energies and oscillator strengths for both the resonance transition 5s2 1S0-5s5p 1P1 and the intercombination lines 5s2 1S0-5s5p 3P1 in the cadmium isoelectronic sequence are computed in an approach which combines limited relativistic configuration mixing to represent intravalence correlation with a polarisation model to account for valence-core correlation. This approach is able to greatly reduce the discrepancies between the theoretical and experimental oscillator strengths for these transitions. A substantial part of the remaining discrepancy, particularly for ionised systems, can probably be attributed to uncertainties in the available experimental data. Systematic trends along the sequence in both the oscillator strengths and in the relative contributions of intravalence and valence-core electron correlation are discussed and compared with those obtained previously for the mercury sequence. It is found that for spin-allowed transitions the share of intravalence correlation increases for lighter (lower Z) homologous systems in corresponding ionisation stages, whereas that of core-valence correlation decreases. For the spin-forbidden transitions, however, both correlation contributions seem to increase for lower Z homologues in the same ionisation stages.