Electron-Molecule Scattering in the Optical-Potential Approach: Surpassing Second Order

This work reports the first application of the many-body optical potential of Bell and Squires beyond second order for electron-molecule scattering. The optical potential is calculated in the two-particle-hole Tamm-Dancoff approximation and the scattering problem solved by use of the Schwinger variational principle. The method is applied to the well-known ${}_{}{}^2{}_{}{}^{}\Pi _{\mathrm{g}}^{}{}_{}{}^{}$ shape resonance of ${\mathrm{N}}_2$ near 2.3 eV, with highly satisfactory results. The importance of including target correlation and polarization in a balanced way is stressed.