DOUBLE PHOTOIONIZATION OF HELIUM: THE HYPERSPHERICAL R-MATRIX
METHOD WITH SEMICLASSICAL OUTGOING WAVES

L Malegat\dag, A Kazansky\ddag and P Selles\dag

\dag Laboratoire de Spectroscopie Atomique et Ionique,
Universit\'e Paris-Sud, Bat. 350, 91405 Orsay,  France

\ddag Institute of Physics, The University of St Petersburg,
St Petersburg, 198904, Russia

We present a novel {\it ab initio} scheme for computing
the wavefunction of the pair of electrons projected into the double
continuum of the helium atom by a one photon dipolar excitation. This
scheme treats the two electrons on the same footing and includes their
mutual repulsion non perturbatively throughout configuration space:
this makes it particularly suitable for the description of the
threshold region where previous methods meet convergence problems.