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A: Atomphysik

THE ROLE OF INITIAL AND FINAL STATE CORRELATION IN DOUBLE IONISATION OF HELIUM — •Bhas Bapat — Fakultät für Physik, Uni-Freiburg, 79104 Freiburg

Double ionisation of helium by the impact of charged particles or photons

has been extensively investigated as a paradigm for the evolution of a

quantum few-body bound state into the continuum. Broadly speaking, this

evolution is believed to be influenced by three separable entities: (a)

the structure of the initial state wavefunction (b) the precise interaction

between the helium atom and the perturbing entity, or "dynamics" (c) the

electron–electron repulsion in the final continuum.

We report on a recent measurement of the momentum spectra of the two electrons

arising from the double ionisation of helium by 100 MeV/u bare carbon ions,

performed with the multi-particle coincidence spectrometer, the "reaction

microscope". From these data, differential cross-sections were obtained. By

comparing these with the results of different model calculations, the three

points mentioned above will be addressed in the talk.