Singlet p-wave elastic electron-positronium scattering*

The photodetachment of Ps^- has been observed [1].

An elaborate calculation of the photodetachment cross section has been

performed using variationally determined wave functions for the ¹S bound state wave and

for the ¹P continuum [2].

Surprisingly, there exists a discrepancy between the photodetachment cross section using these

variational wave functions and the results

from recent theoretical calculations in which the close-coupling [3] and hyperspherical

close coupling [4] methods have been employed for the ¹P continuum state.

Due to this discrepancy we have increased the number of Hylleraas terms in both the

bound-state wave function and in the ¹P electron-positronium scattering wave function (at certain energies) from the number of terms that were used

in the previously variationally determined wave functions [2].

We obtained a better converged binding energy and singlet p-wave phase shifts for very low energies and for an energy just below

the Ps(n=2) threshold than was previously obtained [2].

We plan to show a comparison of the binding energy and the ¹P phase shifts that we obtain

with results from other theoretical calculations.

[1] K. Michishio, T. Tachibana, H. Terabe, A. Igarashi, K. Wada, T. Kuga, A. Yagishita, T. Hyodo, and Y. Nagashima,

Phys. Rev. Lett. 106, 153401 (2011).

[2] S. J. Ward, J. W. Humberston and M. R. C. McDowell, J. Phys. B 30, 127 (1987).

[3] A. Igarashi, S. Nakazaki, and A. Ohsaki, Phys. Rev. A  61, 032710 (2000).

[4] A. Igarashi, I. Shimamura and N. Toshima, New J. Phys. 2, 17 (2000).