Consistency test of double ionization of helium by photons and charged particles

We have performed a consistency test of recent data for the ratios of cross sections of double to single ionization of helium by photons and by fast charged particles. It is based on a relationship that connects the dipole and nondipole components of cross sections by charged particle impact to photoionization and Compton scattering, respectively. We find the high energy ratio ${\mathit{R}}_{\mathit{Z}}$ for charged particles to be a sensitive probe of the photoionization data near threshold. Using recent experimental data for photoionization, the asymptotic ratio ${\mathit{R}}_{\mathit{Z}}$ is found to range from 0.240% to 0.295%, as compared with direct experimental measurement of 0.26%. © 1996 The American Physical Society.