Unnatural parity resonance states in positron-excited hydrogen scattering

Abstract

The coupled-channels optical method for positron scattering has been applied to investigate resonance states with unnatural parities in a positron-excited hydrogen system. The positronium formation channels and continuum channel are included via a complex equivalent local potential. Resonance states with angular momenta L = 1 to L = 2 and parities (−1)L+1 are calculated. Resonance energies and widths are reported and compared with other theoretical calculations. We found that the opening positronium formation channels play an important role in forming nondipole Feshbach resonances.

Plasma-screening effects on positronium formation

“…Positronium (Ps) formation, which is a special rearrangement process in positron-atom collision, has been found to significantly affect the scattering process for low projectile energies in a vacuum. [21][22][23][24][25][26][27][28][29][30] As the screening effect increases in Debye plasmas, the Ps-formation threshold decreases, which results in a more important Ps process at low scattering energies. Moreover, the rate of Ps plays a decisive role in the rate of annihilation and measurement of the spectrum and distribution of the annihilation radiation can provide us with fruitful information to develop our understanding regarding the physical properties of the plasma medium.…”

Natural and Unnatural Parity Resonance States in the Positron-Hydrogen System with Screened Coulomb Interactions

“…Since then, there have been considerable research activities on theoretical calculations of resonances in the positron hydrogen scattering (Refs. [3][4][5][6][7][8][9][10][11][12][13] and references therein). For resonances in positron atom scattering with the target other than the hydrogen atom, considerable theoretical activities have also been reported in the literature (Refs.…”

“…In addition, we have also investigated resonances with unnatural parities (the P-even and D-odd) resonance states with SCP for the first time, to the best of our knowledge. For pure Coulomb cases, resonances with unnatural parities in e + -H system were reported in recent calculations [9][10][11][12][13]. Atomic units are used throughout in the present work.…”