Threshold-energy region in the electron-excitation cross sections of the sodium resonant transition

We present measurements of absolute excitation differential cross sections for electron scattering by ground-state sodium in the 3P manifold at 2.3, 2.4, 2.5, 2.6, 3.0, 3.3, and 3.7 eV in the angular range 1° to 60°. No calibration or normalization procedures are involved. Comparisons with computational results of the close-coupling approximation and experimentally obtained Δ${\mathit{M}}_{\mathit{s}}$- and Δ${\mathit{M}}_{\mathit{L}}$-changing cross sections are made.