Non-perturbative Theory of Atomic Ionization with Two-electron Continuum

A long-term objective of this project is to develop a general method for calculating atomic ionization leading to a final state with two-electron continuum. The theory of such processes should account for the inter-electron interaction between the two outgoing electrons and between each of these electrons with the ion core. A non-perturbative approach to the inter-electron interaction is to be taken by solving the Lippmann-Schwinger equation. The interaction with the core is described within the Hartree-Fock approximation.

Principal Investigator

Anatoli Kheifets
Electron Physics Unit



RFCD Codes


Significant Achievements, Anticipated Outcomes and Future Work

The close-coupling theory of the multiple atomic ionization has been further extended. The role of various correlation mechanisms has been uncovered in double photoionization of the helium atom. The cross-over between the shake-off and two-step mechanisms has been predicted theoretically and confirmed experimentally. The full parametrization of the symmetrized double photoionization amplitudes has been achieved offering a general description of the double photoionization process at a very wide range of photon energies and geometries of the two-electron escape. The second-order corrections to the electron impact ionization have been estimated in the double ionization of the helium atom.


Computational Techniques Used

The code has been ported from SGI to the Compaq AlphaServer SC. It was linked to the Compaq Extended Math Library (parallel routines). The code has been compiled using -omp multiprocessor option. With these modifications a two-fold gain in speed was achieved as compared to the SGI.


Publications, Awards and External Funding

A. S. Kheifets, I. Bray, J. Berakdar, and C. Dal Cappello. Comparative theoretical study of (e, 3e) on helium: Coulomb-waves versus close-coupling approach. J. Phys. B, 35(1):L15--L21, 2002.

A. Dorn, A. Kheifets, C. D. Schroeter, B. Najjari, C. Hoehr, R. Moshammer, and J. Ullrich. Double ionization of helium by electron-impact in the impulsive regime. Phys. Rev. A, 65(2):115202, 2002.

G. Turri, L. Avaldi, P. Bolognesi, R. Camilloni, M. Coreno, G. Stefani, J. Berakdar, and A.S. Kheifets. Photodouble ionisation of He at 80 eV excess energy in equal energy sharing condition. Phys. Rev. A, 65(3):4702, 2002.

A. S. Kheifets and I. Bray. Frozen core model of the double photoionization of beryllium. Phys. Rev. A, 65(1):2710, 2002.

A. S. Kheifets and I. Bray. Symmetrized amplitudes of the helium atom double photoionization. Phys. Rev. A, 65(2):2708, 2002.

C. Dawson, S. Cvejanovic, D. P. Seccombe, T. J. Reddish, F. Maulbetsch, A. Huetz, J. Mazeau, and A. S. Kheifets. Helium (gamma,2e) triple differential cross sections at an excess energy of 60 eV. J. Phys. B, 34(16):L525--L533, 2001.

P. Bolognesi, R. Camilloni, M. Coreno, G. Turri, J. Berakdar, A.S. Kheifets, and L. Avaldi. Complementary TDCS for the photo-double ionisation of He at 40 eV above threshold in unequal energy sharing conditions. J. Phys. B, 34(15):3193--3203, 2001.

A. Lahmam-Bennani, A. Duguet, M. N. Gaboriaud, I. Taouil, M. Lecas, A. S. Kheifets, J. Berakdar, and C. Dal Cappello. Complete experiments for the double ionisation of He: (e,3e) cross sections at 1 keV impact energy and small momentum transfer. J. Phys. B, 34(15):3073--3087, 2001.

A. S. Kheifets. On different mechanisms of the two-electron atomic photoionization. J. Phys. B, 34(8):L247--L252, 2001.

A. Dorn, A. Kheifets, C. D. Schroeter, B. Najjari, C. Hoehr, R. Moshammer, and J. Ullrich. Double ionization of helium by electron-impact: Complete pictures of the four-body break up dynamics. Phys. Rev. Lett., 86(17):3755--3758, 2001.