Dynamic scaling of photo-double-ionization to electron impact

We employ an ab initio theory to address several inconsistencies of the empirical scaling of photo-double-ionization (PDI) to electron impact ionization suggested by Samson [Phys. Rev. Lett. 65, 2861 (1990)10.1103/PhysRevLett.65.2861]. We do so (i) by isolating the only relevant dipole component of the electron impact ionization and (ii) by replacing the static scaling of Samson, who used an effective cross-section area of the ion remainder, with dynamic scaling using the squared momentum of the photoelectron. The modified scaling is tested in the He 1s2 isoelectronic sequence and the combined inner shell 1s and valence shell 2p PDI of the negative F-ion [Müller et al., Phys. Rev. Lett. 120, 133202 (2018)10.1103/PhysRevLett.120.133202].