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.
Quantum defect theory for the study of hadronic atoms
Quantum defect theory can be used to convert energy shifts of hadronic atoms into zero-energy scattering lengths (and vice versa). The scattering lengths from quantum defect theory are in good agreement with those derived using all-order Deser-Trueman formulae (evaluated by the simple expedient of evaluating the left-hand side of the effective range expansion exactly). Scattering lengths derived from experimental energy shifts are presented for a number of hadronic atoms.