Geometric shielding correction approach for total cross sections of electron scattering by C6H6, C6F6, C6H12, C6H14, C6F14, C8H16, C8H18 and C8F18 at 30-5000 eV

Taking into consideration the contributions of the geometric shielding effect in the molecule, 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. The total cross sections for electron scattering by eight larger polyatomic molecules (C6H6, C6F6, C6H12, C6H14, C8H16, C8H18, C6F14 and C8F18) are calculated using the new additivity rule at the Hartree-Fock level for impact energies ranging from 30 to 5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories, and good agreement is attained above 100 eV or so. The new results for C6F14 and C8F18 are also presented although no experimental and theoretical data are available for comparison in the present energy region. In these calculations, the atoms are represented by the spherical complex optical potential, which is composed of static, exchange, polarization and absorption terms.