Birgit Lohmann#, A. Duguet=86, A. Lahmam-Bennani=86, I. Taouil=86, J.=
 Rasch=87, C.
T. Whelan* and H. R. J. Walters=A7

#School of Science, Griffith University, Nathan Queensland 4111 AUSTRALIA
=86Laboratoire des Collisions Atomiques et Mol=E9culaires, B=E2t. 351, Unive=
de Paris XI,=20
F-91405 Orsay Cedex FRANCE
=87Institut de Physique, Universit=E9 de Metz, Rue Arago, 57078 Metz Cedex 3
*Dept. of Applied Mathematics and Theoretical Physics, Cambridge
University, CB3 9EW UK
=A7Dept. of Applied Mathematics and Theoretical Physics, The Queen's
University, Belfast BT7 1NN UK

(e,2e) measurements for Ar(2p) ionization under highly asymmetric
kinematics are presented. The kinematics correspond to a low momentum
transfer of 0.5 a.u., however despite this the cross section is not
symmetric about the momentum transfer direction, K. The results are
compared with first Born and distorted wave Born approximation (DWBA)
calculations. The two calculations both predict symmetry about K, in
disagreement with what is experimentally observed. It is suggested that a
new mechanism must be invoked to explain the data.