Speaker
Description
Bound states of positrons with small neutral atoms have not yet been detected experimentally. However, they are expected to have very small positron affinities. Not only does this pose a challenge for modeling such states reliably, but it also raises a question of how important the relativistic effects are and whether they can alter the dynamical stability of the weakly bound positron-atom complexes.In the framework of the variational method we have carried out new improved calculations of three bound states of positronic beryllium. Using large expansions in terms of explicitly correlated Gaussians we generated accurate nonrelativistic wave functions and determined some structural properties and annihilation rates. Next, we investigated the leading-order relativistic effects in all three bound states of positronic beryllium. Our conclusion is that neither the inclusion of scalar relativistic nor spin-dependent corrections alter the predictions regarding the existence of the bound states. When leading-order relativistic effects are taken into account, positron affinities change by about 2% or less. This is so even for the triplet P state of positronic beryllium, where the spin--orbit correction is not at all canceled out when the energy difference with the parent system is computed.
