PHOTOIONIZATION CROSS-SECTIONS OF HE AND H-2

We combine accurate measurements at low energies and theoretical calcu lations at high energies to construct sets of photoionization cross se ctions of He and H-2 that should be reliable at all energies. We contr ol the accuracy of the recommended cross section data by ensuring that they satisfy a range of oscillator strength sum rules. We provide acc urate analytic formulae for the photoionization cross sections that ha ve the proper asymptotic form. At high frequencies the cross sections for H-2 are 2.8 times those for H.