On the reliability of the SCF and CI wavefunctions for systems containing positrons

The energies and electron—positron collision probabilities for complexes of a positron with one- and two-electron atoms of variable nuclear charge have been studied. In the case of a one-electron atom quantum chemical calculations within the correlated functions approach have also been performed. The results obtained suggest that the energy of the complex can be reproduced relatively well at the CI level, but it requires the use of a flexible basis set. However, it is practically imposible to obtain reliable values of the collision probability. An alternative method of estimation of the electron—positron collision probability has been proposed. It is based on an equation relating the cusp value with the relevant collision probability.