Electron-impact ionization of helium: A comprehensive experiment benchmarks theory

Single ionization of helium by 70.6-eV electron impact is studied in a comprehensive experiment covering a major part of the entire collision kinematics and the full 4{π} solid angle for the emitted electron. The absolutely normalized triple-differential experimental cross sections are compared with results from the convergent close-coupling (CCC) and the time-dependent close-coupling (TDCC) theories. Whereas excellent agreement with the TDCC prediction is only found for equal energy sharing, the CCC calculations are in excellent agreement with essentially all experimentally observed dynamical features, including the absolute magnitude of the cross sections.