Integrated cross sections for the electron-impact excitation of ground-state hydrogen to the 3s, 3p, and 3d final states have been calculated using propagating exterior complex scaling and convergent close-coupling methods at energies between the n=3 and 4 excitation thresholds. The calculations are in excellent agreement and demonstrate that exterior complex scaling methods can accurately reproduce the resonance structure and magnitude of the excitation cross sections below the ionization threshold. Measurements of the separate 3s, 3p, and 3d differential cross sections were made at 12.24 eV, and are consistent with both calculations within a total experimental uncertainty of about 35%.
Bartlett, P. L., Williams, J., Bray, I., Mikosza, A., & Stelbovics, A. T. (2006). Differential and integrated cross sections for excitation to the 3s, 3p, and 3d states of atomic hydrogen by electron impact below the n=4 threshold. Physical Review A, 74(2), Article number 022714. https://doi.org/10.1103/PhysRevA.74.022714