Elastic scattering of electrons by polyatomic molecules in the energy range 300-1300 eV: CO, CO2, CH4, C2H4 and C2H6

Differential cross sections (DCS) for the elastic scattering of electrons h ave been measured by the crossed-beam technique for CO, CO2, CH4, C2H4 and C2H6 in the angular range 30 degrees-120 degrees and at impact energies of 300, 500, 700, 900, 1100 and 1300eV. The measurements were made with a view to test the validity of the independent atom model (IAM) for polyatomic mo lecules in this energy region. A comparison of experimental results with th e IAM calculations indicates that the model is adequate for the linear mole cules CO and CO2 in the energy region 900-1300 eV. The Born approximation f or the evaluation of the atomic scattering amplitudes was found to be valid only at 1300 eV for all the molecules except for C2H6. A survey of the pre vious experimental and theoretical data based on different models shows tha t proper molecular wavefunctions have to be used for the evaluation of shor t-range potentials and that valence-bond distortion, absorption and non-adi abatic effects in the polarization potential have to be considered.