Lowest lying doubly-excited P-and D-state resonances of Ps⁻ in weakly coupled plasmas

Abstract.

The lowest-lying ^{1, 3}P^o and ¹D^e resonances of positronium negative ion, Ps⁻, in weakly coupled plasmas have been investigated employing the close-coupling approximation. Three different basis sets have been employed in the present study. The plasma screening condition obtained from the Debye-Hückel type potential is used to represent the interaction between the charged particles. The resonance energies and the corresponding widths of one ¹P^o, two ³P^o, and one ¹D^e resonant states associated with the n = 2 threshold of the positronium atom for various Debye lengths ranging from infinity to small values are reported. The ¹P^o resonance as well as the higher lying ³P^o resonant state transforms to a shape resonance for denser plasma conditions. The ¹D^e resonant state also changes to a shape-type resonance for very dense plasmas.