Using a variational method with an explicitly correlated Gaussian basis, we study the $e^{+}$-Li and $e^{+}$-Be complexes in the ground and lowest excited states with higher spin multiplicity. Our calculations provide rigorous theoretical confirmation that a positron can be attached to the excited states: $1s2s2p{}^{4}P^o$ and $1s^{2}2s2p{}^{3}P^o$ for $e^{+}$-Li and $e^{+}$-Be, respectively. The result is particularly notable for the $e^{+}$-Be complex, as the excited ${}^{3}P^o$ state lies below the autoionization threshold. We report accurate binding energies, annihilation rates and structural properties of these positron-atom systems. The existence of the ground and metastable excited states with bound positron opens up a new route to the presently lacking experimental verification of stability of a positron binding to any neutral atom.

• Received 31 July 2013

DOI:https://doi.org/10.1103/PhysRevLett.111.193401