The production of the projectile $2s2p{}^{3}P$ and $2s2p{}^{1}P$ autoionizing states is investigated in 0.5–1.5 MeV/u collisions of He-like carbon and oxygen mixed-state three-component $(1s^2,1s2s{}^{3}S,1s2s{}^{1}S)$ ion beams with helium targets. The mixed-state beams are produced in the stripping systems of the 5.5-MV Demokritos tandem accelerator. Using high-resolution Auger projectile electron spectroscopy, the normalized Auger electron yields are measured at $0^{\circ }$ relative to the beam direction. In addition, a three-electron atomic orbital close-coupling approach, employing full configuration interaction and antisymmetrization of the three-electron, two-center total wave function, is applied to calculate the production cross sections for these states from each of the three initial ion beam components. Thereupon, the theoretical Auger yields are computed and found to be mostly smaller than experiment by factors ranging from near 1 to about 10. Agreement, however, improves when larger $1s2s{}^{1}S$ fractions, not only based on spin statistics, are projected. Overall, we present a careful and sophisticated analysis with a thorough discussion of these results which show that our current understanding is still incomplete. Nevertheless, our nonperturbative excitation treatment—free from scaling parameters and renormalization—marks a significant advancement in modeling ultrafast multielectron dynamics within open-shell quantum systems.

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• Atomic & molecular collisions
• Atomic & molecular structure
• Atomic spectra
• Autoionization & Auger processes
• Electronic excitation & ionization
• Electronic transitions