Interplay of initial and final states for (gamma,2e) and (e,3e) processes on helium

L. U. ANCARANI; GUSTAVO GASANEO; F. D. COLAVECCHIA; C. DAL CAPPELLO

PHYSICAL REVIEW A - ATOMIC, MOLECULAR AND OPTICAL PHYSICS

American Physical Society

Lugar: New York; Año: 2008 p. 627121 - 6271212

1050-2947

The role of the description of initial and final states in (γ,2e) and high incident energy (e,3e) collisions with helium targets is investigated. We describe the double continuum as a product of plane waves modulated by three Coulomb distortion factors and propose different sets of initial states which satisfy exactly all two-body Kato cusp conditions. Wave functions with only angular correlation, and with both angular and radial correlation, are considered; in each case, the interparticle correlation factors are such that they have different (polynomial, exponentially increasing or decreasing, and oscillatory) asymptotic behaviors. The gauge discrepancies observed in (γ,2e) calculations show that the overall agreement with absolute (e,3e) experimental data at 10+10 eV ejected energy obtained with simple initial states is fortuitous and can hardly be attributed to a balanced description with respect to the final state. Thus the description of the final state by the product of plane waves and three Coulomb distortion factors is not suitable to describe sufficiently well the double continuum of two electrons ejected at 10 eV. An investigation of the ejected energy dependence on both double ionization processes further illustrates that what is observed at 10+10 eV ejected energy does not necessarily hold at higher values. Further theoretical studies and new experimental data are clearly needed to help understand the interplay of initial and final states.