PHOTOIONIZATION BY PHOTOABSORPTION OF A TWO--ELECTRON ATOM OR ION AND THE PROPERTIES OF THE TWO--ELECTRON WAVE FUNCTIONS T. Suri\'{c}$^{*}$, R. H. Pratt$^{\dag}$ and E. G. Drukarev$^{\ddag}$ $^{*}$R. Bo\v{s}kovi\'{c} Institute, Zagreb, Croatia $^{\dag}$University of Pittsburgh, Pittsburgh, PA, USA $^{\ddag}$Petersburg Nuclear Physics Institute, St. Petersburg, Russia We describe within a unified nonrelativistic approach single and double photoionization of two electron atoms by photoabsorption at high photon energies $\omega$ (but still $\omega \ll m$). The singularities of the Coulombic interactions (e--e and e--N) determine the high energy behavior of the processes and in the case of double ionization explain the shake--off and quasi--free contributions at high energies, and in single ionization explain deviations from IPA predictions.