High-energy dependence of the molecular-hydrogen photoionization cross section

The photoionization cross section for H₂ per atom has recently been reported to be ∼ 45% larger than the atomic cross section at energies of 5.41 and 8.39 keV. This note relates this observation to the differences in electron density at the nucleus in atomic and molecular hydrogen and points out that the enhancement at high photon energies is unique for molecular hydrogen.