Scattering cross sections for slow electrons in polyatomic gases

Momentum transfer and inelastic collision cross sections for electrons in CO, N 2 O and CO 2 have been calculated in the energy range 0.01 to 0.1 eV. The effective-range theory and the Born approximation have been used to calculate respectively the elastic and inelastic cross sections. The scattering lengths have been found to be approximately -1.12 a 0 , -3.7 a 0 and -7.2 a 0 for CO, N 2 O and CO 2 respectively. The calculated rotational transition cross section for CO at electron energies below vibrational threshold is in very good agreement with the experimental value. The importance of the quadrupole interaction and the other branches of the potential function has been discussed.