Angular correlation in the two-electron continuum of the helium
double photoionization

S. Cvejanovi\'c$^\dagger$, J. P. Wightman$^\dagger$,
T.J.Reddish$^\dagger$, F. Maulbetsch$^\dagger$,
M. A. MacDonald$^\ddagger$, A.S. Kheifets$^\star$ and I. Bray$^\sharp$

$^\dagger$Physics Department, The University of Newcastle,
Newcastle-upon-Tyne NE1 7RU, UK

$^\ddagger$CLRC, Daresbury Laboratory, Daresbury, Warrington WA4 4AD,
UK

$^\star$Research School of Physical Sciences and
Engineering, Australian National University, Canberra A.C.T. 0200,
Australia.

$^\sharp$Electronic Structure of Materials Centre, Flinders University
of South Australia, GPO Box 2100, Adelaide S.A. 5001, Australia

Angular correlation in the two-electron continuum of the He double
photoionization has been studied, both experimentally and
theoretically, at equal and unequal energy sharings at the photon
energies of 20 and 40~eV above the threshold.  Good agreement has been
found between theory and experiment in most cases except for the
unequal energy sharing when one of the escaping electrons is detected
in the direction close to the polarization axis of the linearly
polarized light