LOW-ENERGY TRIPLE DIFFERENTIAL CROSS-SECTIONS FOR ELECTRON-IMPACT IONIZATION OF HELIUM

The BBK model is modified by the introduction of effective Sommerfeld parameters for both symmetric and asymmetric geometries on an empirica l basis, while still maintaining the philosophy that all three Coulomb interactions are included on an equal footing. The triple differentia l cross sections for electron-impact ionization of atomic helium at an incident energy of 40 eV in an asymmetric geometry are calculated. Re sults of this approach are compared with the absolute measurements and the only existing theoretical results of the convergent close-couplin g method.