Detailed theoretical and experimental analysis of low-energy electron-N2 scattering.

We have carried out a comprehensive theoretical and experimental study of electron scattering from molecular nitrogen at energies below 10.0 eV. In the theoretical component of this project we have generated differential and integral cross sections for elastic scattering and vibrational excitation in converged vibrational close-coupling calculations. In the experiments, we have measured differential cross sections for these processes at scattering angles from 20\ifmmode^\circ\else\textdegree\fi{} to 130\ifmmode^\circ\else\textdegree\fi{} in a crossed-beam experiment at a large number of energies between 0.55 and 10 eV and, in a complementary time-of-flight experiment, total cross sections at energies between 0.08 and 10.0 eV. The measured angular distributions have been extrapolated to 0\ifmmode^\circ\else\textdegree\fi{} and 180\ifmmode^\circ\else\textdegree\fi{} using a procedure based on a nonlinear least-squares fit constrained by known physical properties of the e-${\mathrm{N}}_{2}$ scattering matrix; numerical integration of the resulting extrapolated distributions yields integrated cross sections with almost no error beyond that inherent in the measured angular data. We find generally good agreement between the present experimental and theoretical cross section, particularly at energies near the ${\mathrm{\ensuremath{\Pi}}}_{\mathit{g}}$ resonance near 2.39 eV. In previous studies of scattering in this region, such comparisons have been made problematical by the difficulty of ascertaining the appropriate theoretical scattering energy. We recommend here a protocol for resolving this problem for both elastic scattering and vibrational excitation.