Alternative vibrational frame transformation for electron-molecule scattering

An energy-dependent vibrational frame transformation for electron-molecule scattering is reformulated to account for a class of nonadiabatic effects resulting when the electron time delay in the reaction zone is appreciable. The electron-molecule compound system is described by a special class of Born-Oppenheimer eigenstates, singled out by requiring their nuclear vibrational wave functions to coincide with those of the molecular target. Combined with the multichannel quantum defect theory, this treatment describes resonant and nonresonant electron-molecule scattering near threshold equally well, as well as molecular Rydberg spectra.