Complex-coordinate calculations of doubly excited 1,3De resonant states of Ps-

Abstract

Doubly excited $^{1,3}$${\mathit{D}}^{\mathit{e}}$ resonant states in positronium ions ${\mathrm{Ps}}^{\mathrm{\ensuremath{-}}}$ are calculated by using a method of complex-coordinate rotation. Resonance parameters (both resonance positions and widths) for doubly excited states associated with the n=2 and 3 thresholds of positronium atoms are evaluated using elaborate Hylleraas-type functions. In addition to Feshbach-type resonances lying below the Ps thresholds, we have also identified two $^{1}$${\mathit{D}}^{\mathit{e}}$ shape resonances lying above the n=3 Ps threshold.