Thermal conformational averaging effects in low-energy electron scattering from β -alanine

Low-energy electron scattering from the ten conformers of gas-phase β-alanine is investigated using the Schwinger multichannel method within the static-exchange and static-exchange plus polarization approximations. Born-closure corrections are included to account for long-range electron-dipole interactions, and thermally averaged integral cross sections are obtained from Boltzmann populations derived from Gibbs free energies. All conformers exhibit a low-energy π* shape resonance associated with temporary occupation of a carboxyl-centered antibonding orbital, as confirmed by Dyson-orbital analysis. Although the resonance energies show only small conformer-to-conformer variations, the elastic integral cross sections depend strongly on the permanent molecular dipole after inclusion of the Born correction. Consequently, thermal averaging has little influence on the resonance position but significantly affects the absolute cross section magnitude through the temperature-dependent conformer populations. Comparison with previous R-matrix calculations shows good overall agreement for the resonance pattern and the thermally averaged scattering profiles. These results demonstrate that conformational flexibility affects local and global scattering properties in fundamentally different ways: the resonance is dictated by the local electronic structure of the carboxyl group, whereas the elastic cross section is governed primarily by long-range electron-dipole interactions.