Doubly Excited 1,3 P e Resonance States of the Positronium Negative Ion with Coulomb and Screened Coulomb Potentials

Abstract

We have investigated the doubly excited 1,3Pe resonance states of positronium negative ion with Coulomb and screened Coulomb potentials using highly accurate correlated exponential wavefunctions. For Coulomb interaction, the stabilization and the complex-rotation methods are employed to extract resonance parameters (resonance positions and widths). We have obtained two 1Pe resonances and three 3Pe resonances below the n = 3 Ps threshold. In addition to Feshbach resonances lying below n = 3 Ps threshold, we have calculated one 3Pe shape resonances lying above the Ps (n = 2) threshold. For screened Coulomb (Yukawa) interaction, we employ the stabilization method to extract resonance parameters as functions screening parameter. The resonance energies and widths for 1,3Pe resonance states of Ps− below the n = 3 Ps threshold for different screening parameters ranging from infinity (Coulomb case) to small values are reported, along with the Ps(3S) and Ps(3P) threshold energies. The screened Coulomb results for the 1,3Pe resonance states are reported for the first time in the literature.