Geometric shielding corrections for calculation of electron scattering by CO2C2H2, CHCl3, CH2C2, CH3Cl, CHF3, CH2F2 and CH3F at 30-5000 eV

Taking into account the changes of the geometric shielding effect in a molecule as the incident electron energy varies, an empirical fraction, which depends on the energy of the incident electrons, the target's molecular dimension and the atomic and electronic numbers in the molecule, is presented. Using this empirical fraction, a new formulation of the additivity rule is proposed. Using the new additivity rule, the total cross sections of electron scattering by CO2 C2H2, CHCl3, CH2C2, CH3Cl, CHF3, CH2F2 and CH3F are calculated at the Hartree-Fork level at 30-5000eV. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is obtained over a wide energy range, especially above 100eV. (c) 2008 Elsevier Ltd. All rights reserved.