Energy and angular resolved studies of double photoionization of helium and rare gases

Experiments on double photoionization, where the two outgoing electrons are selected in angle and energy before being detected in coincidence, have started in 1991 on xenon and krypton. During the past four years they have been extended to lighter rare gases including helium, and a general understanding of the observed angular patterns has started to emerge. In the present paper we report on such recent measurements in helium, neon and argon, obtained with a multidetection apparatus and in the so called ''coplanar'' geometry. We try to analyse the physical effects underlying the shapes of the various angular patterns which are presented