Superelastic scattering, a collision process in which the scattered electron gains energy, has been investigated for metastable C4+(1s2s 3S) and O6+(1s2s 3S) He-like ions colliding with quasifree H2-target electrons. The measured superelastic-scattering cross sections for 1s2s 3S-->1s2 1S deexcitation show a strong dependence on the collision energy and the atomic number of the He-like ion. R-matrix calculations for the time-reversed equivalent process of electron-impact excitation are compared with the measured cross sections through the principle of detailed balance. In these calculations, the impulse approximation is utilized in conjunction with the Compton profile of the target electrons for the collisions of ions with quasifree electrons studied here. Calculations were performed taking into account the anisotropy of the cross sections as a function of the scattering angle, which equals 180° in the projectile rest frame for the reported measurements. Comparison between theory and experiment was used to infer the metastable 1s2s 3S fraction in the incident He-like beam.
Physical Review A
- Pub Date:
- April 2002
- Electronic excitation and ionization of atoms;
- Atomic excitation and ionization by electron impact;
- Electron-ion scattering;
- excitation and ionization