Calculation of resonance states of positronic lithium atom

Abstract: Feshbach resonance states of positronic lithium atom are precisely calculated with aGaussian expansion method. By adopting a Lorentzian formula for density of state,resonance energies and widths are systematically determined from series of energy levelscalculated by a real scaling method. We identify Feshbach resonance states between Li(2p)+ e⁺and Li (4s) + e⁺thresholds and the results arein good agreement with previous works with the real scaling method and complex scalingmethod. Our results of a dipole series of resonances supported by ion-dipole interactionof Li⁺-Ps(n = 2),whose existence has been pointed out by previous works, show a good agreement with thelatest calculation with a complex scaling calculation. We point out that an accuracy ofthe model potential for the electron and positron from the atomic ion is significant forthe positronic atom formation process. Graphical abstract: [Figure not available: see fulltext.]