  The importance of the excited states of Positronium (Ps) in the formation
cross sections(both differential and total) of the negative hydrogen ion (H^-)
are investigated theoretically for the charge transfer reaction, Ps (n = 1, 2)
+ H --> e+ + H^- for a wide range of incident energies (e. g., threshold - 500
eV) . The calculations are performed in the frame work of a qualitative model,
the post collisional Coulomb Modified Eikonal Approximation (CMEA) . A
comparative study is also made between the capture from ground and excited
states of the Ps. The present CMEA model takes account of higher order effects
which is essential for a rearrangement process where the First Born type
Approximation (Coulomb Born for the ionic case) is not supposed to be adequate.
At low incident energies, the excited states of Ps (2s, 2p) are found to play a
dominant role in the H^- formation cross sections . Significant deviations are
noted between the present CMEA and the Coulomb Born (CBA) results even at very
high incident energies (e.g., Ei = 500 eV), indicating the importance of higher
order effects. At high incident energies the present CMEA differential cross
section (DCS) exhibits a double peak structure which is totally absent in the
CBA and could again be attributed to higher order effects.
