Electron-impact ionization of atomic hydrogen: Comparison of asymmetric (e,2e) measurements with theories

Differential cross sections have been measured for the electron-impact ionization of atomic hydrogen, using the ($e$, $2e$) technique with coplanar asymmetric kinematics. The experiments were performed at an incident energy of 250 eV with the slow outgoing electron being detected at energies of 5, 10, and 14 eV, for scattering angles of the fast outgoing electron of 3°, 5°, and 8°. The data are compared with differential cross sections calculated with use of the factorized distorted-wave impulse approximation, the plane-wave impulse approximation, and three recent Born-approximation calculations, consisting of first-order Born, second-order Born, and eikonal Born series treatments. In the distorted-wave impulse approximation calculations we investigate the effect of using different descriptions for the fast outgoing electron. Comparison of the data and the calculated cross sections indicates reasonable agreement with the distorted-wave impulse calculations, and good agreement with the second-order and eikonal Born series calculations.