Electron scattering with and without vibrational excitation. VIII. Comment on a theory of small-energy-transfer collisions dominated by long-range forces

Two methods [D. G. Truhlar and J. K. Rice, J. Chem. Phys. 52, 4480 (1970)] and B. Ritchie, Phys. Rev. A 6, 1456 (1972)] for calculating cross sections for vibrational excitation of molecules by electron impact are compared. The former method is shown to have a greater range of applicability. Cross sections computed by the two methods differ by about a factor of 2 for excitation to the first vibrationally excited level of H2. The neglect of the short-range potential in Ritchie's method is shown to be an important source of error in that method.