Isoelectronic study of triply excited Li-like states

Absolute doubly differential cross sections (DDCSs) for the production and Auger decay of the intra-shell 2s2p^2 2D triply excited state formed in collisions of He-like ions (Z = 5–9) with H₂ were determined experimentally, using zero-degree Auger projectile electron spectroscopy. The ²D^e state was directly produced by 180° resonant scattering of the quasi-free H₂ electrons from the 1s2s ³S metastable state of the ion. Resonant energies and DDCSs calculated using the R-matrix approach within the electron scattering model were found to be in good overall agreement with experiment.