Research Article
Projectile Excitation to the 2s2p³P and ¹P Autoionizing States in Swift Collisions of He-Like Carbon and Oxygen Mixed-State (1s², 1s2s ³S) Ion Beams With Helium
The production of the projectile 2s2p3P and 2s2p1P autoionizing states is investigated in 0.5-1.5 MeV/u collisions of He-like carbon and oxygen mixed-state three-component (1s2,1s2s3S,1s2s1S) 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∘ 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 smaller than experiment by factors ranging from about 1.2 to 7.6. Agreement, however, improves when larger 1s2s1S fractions, not only based on spin statistics, are projected. Overall, this non-perturbative treatment of excitation, which does not rely on scaling parameters or renormalization, marks a significant advancement in the modeling of multielectron, multi-open-shell quantum systems subjected to ultrafast perturbations, where current understanding remains incomplete.
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