Positronic complexes with unnatural parity

Abstract

The structure of the unnatural parity states of PsH, LiPs, NaPs, and KPs are investigated with the configuration interaction and stochastic variational methods. The binding energies (in hartree) are found to be $8.17\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, $4.42\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, $15.14\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, and $21.80\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$, respectively. These states are constructed by first coupling the two electrons into a configuration which is predominantly $^{3}P^{e}$, and then adding a $p$-wave positron. All the active particles are in states in which the relative angular momentum between any pair of particles is at least $L=1$. The LiPs state is Borromean since there are no three-body bound subsystems (of the correct symmetry) of the (${\mathrm{Li}}^{+}$, ${e}^{\ensuremath{-}}$, ${e}^{\ensuremath{-}}$, ${e}^{+}$) particles that make up the system. The dominant decay mode of these states will be radiative decay into a configuration that autoionizes or undergoes positron annihilation.