Simple procedure for including vibrational effects in the calculation of electron-molecule cross sections

The widely used rigid-rotor approximation of low-energy electron-molecule scattering theory neglects completely the vibrational motion of the target. The errors this approximation introduces into calculated elastic and rotational-excitation cross sections are larger than other sources of imprecision in present state-of-the-art electron-molecule collision studies. We have applied an alternative to the rigid-rotor approximation: an extremely simple vibrational averaging of the interaction potential. This procedure reintroduces effects due to the zero-point vibrational motion without incurring in the solution of the Schroedinger equation computational demands beyond those of a rigid-rotor calculation. Tests on {ital e}-H{sub 2} and {ital e}-N{sub 2} scattering demonstrate the improved accuracy and computational efficiency that results from vibrational averaging.