Professor Anatoli Kheifets
Atomic and Molecular Physics Laboratories

The process of non-sequential single-photon double ionization, and a closely related process of double ionization by a fast charged particle impact, both involve single interaction of the projectile with a target which results in simultaneous change of quantum states of two or more target electrons. These are fundamentally important processes as they constitute a direct probe of many-electron correlation, either in the initial bound state or the final multiply ionized state. The bound state correlation is a static process which can be described relatively easily by various configuration-interaction schemes. Dynamical correlation in the multi-particle continuum is much more difficult to describe theoretically. Due to a long range of the Coulomb interaction, the continuum correlation cannot be treated perturbatively and a non-perturbative approach has to be taken.

A two-particle continuum state can be treated very efficiently by the convergent close-coupling (CCC) method in which one of the particles is represented by a complete set of discrete (positive and negative energy) Laguerre basis pseudostates while the second particle is treated as a true continuum state. Details of the CCC method and its application to correlated multiple ionization processes will be presented.

Bibliography:
I. Bray, D. V. Fursa, A. S. Kadyrov, A. T. Stelbovics and A. S. Kheifets
Electron- and photon-impact atomic ionization
Physics Reports 520, 135 (2012)