POSITRON-ALKALI COLLISIONS WITH POSITRONIUM FORMATION AT
INTERMEDIATE AND HIGH ENERGIES

O. A. Foj=A2n*, R. Gayet+, J. Hanssen#, P. A. Hervieux# and R.D. Rivarola*

* Instituto de F=A1sica Rosario (CONICET-UNR), Av. Pellegrini 250, (2000)
Rosario, Argentina

+ Centre de Physique Th=82orique et de Mod=82lisations, Universit=82 de Bor=
deaux
I, Talence, France

# Laboratoire de Physique Mol=82culaire et des Collisions, Institut de
Physique Rue Arago, T=82chnop=93le 2000, Metz, France

In this work, positronium formation through electron capture from ground
state alkali targets is studied at intermediate and high impact energies
by means of a distorted wave model.  In particular, the interest is
focused on electron capture from the inner shells of the target. Total
cross sections are computed for several alkali targets and a comparison
with other theories and experimental results is given.  As expected from
matching velocity arguments, as the impact energy increases the formation
cross section is dominated by capture from the inner shells of the target.=
=20