GEOMETRIC SHIELDING EFFECTS OF ELECTRON-SCATTERING FROM POLYATOMIC-MOLECULES

Considering the changes of the shielding effect in molecules as the en ergy of the incident electrons is varied, we present a new modified ad ditivity rule based on the additivity rule of Bobeldijk, van der Zande and Kistemaker [Chem. Phys. 179 (1994) 125], used earlier. The new mo dified additivity rule, which relates to molecular geometric propertie s and the energy of the incident electrons, is employed to calculate t otal cross sections (TCSs) for electron scattering from CO2, N2O, CS2, NH3 and SF6 molecules in the range 30-1000 eV. Compared with other ad ditivity rule results, the present approach for the TCS on polyatomic molecules is simple but more effective and it yields better agreement with experiments in the intermediate-and high-energy region, in partic ular for complex polyatomic molecules. (C) 1997 Elsevier Science B.V.