STSM by Tor Kjellsson, Stockholm University (SE) with  Luca Argenti and Fernando Martín, Universidad Autonoma de Madrid (ES)
On May 4th, 2014 (19 days)
From SWEDEN to SPAINSU_logo UAM_logo

Time-dependent atomic photoionisation with a Multi-Configuration-Hartree-Fock close-coupling approach

The most critical aspect in understanding electronic motion in matter is the phenomenon called correlation – the collective dynamics of the electrons by which they manage to lower the total energy of the system by avoiding each other. While being of utmost interest to understand, correlation is generally computationally demanding to describe. To account for it during a dynamic process such as ionization is particularly challenging and this problem is the focus of the program package currently being developed in Stockholm and Madrid in collaboration. The program will eventually be able to solve the time-dependent Schrödinger equation (TDSE) for arbitrary manyelectron atoms under the action of pulsed fields and builds on a multi-reference Hartree-Fock close-coupling ansatz.
The main objectives that were carried out during the present STSM were to test the recently added parallel solver as well as implementing an analyser for the output from it. For this analyser we wrote a program that calculates the partial photoelectron spectra dP
/dE, dependent on the  symmetry and the ionization channel index, of the wave packets generated by the TDSE program, based on the projection on a set of scattering states. The scattering states are obtained in terms of a discretized solution to the multi-channel Lippmann-Schwinger equation.
The analyser was successfully tested on helium against a separate two-active-electron program that is known to work correctly.
With these additions a large step towards finalizing the program was taken. When ready, the program will be able to give a theoretical description of realistic attosecond pump-probe experiments that quantitatively accounts for the parent-ion rearrangement during a photoionization event.

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