8 research outputs found
Electronic correlations in double ionization of atoms in pump-probe experiments
The ionization dynamics of a two-electron atom in an attosecond XUV-infrared
pump-probe experiment is simulated by solving the time-dependent two-electron
Schr\"odinger equation. A dramatic change of the double ionization (DI) yield
with variation of the pump-probe delay is reported and the governing role of
electron-electron correlations is shown. The results allow for a direct control
of the DI yield and of the relative strength of double and single ionization
Quantum breathing mode of trapped bosons and fermions at arbitrary coupling
An analysis of the quantum breathing behavior of few-particle Coulomb systems
in one- and two-dimensional harmonic traps is presented. We report the
existence of \emph{two independent breathing modes} and present exact numerical
results for two particles at any coupling strength which smoothly connect the
two known limits of an \emph {ideal} quantum and a strongly coupled \emph
{classical} system. Substantial differences in the breathing frequency of
two-dimensional fermions and bosons are observed which may be used as a
sensitive experimental tool to probe confined interacting quantum systems
Efficient grid-based method in nonequilibrium Green's function calculations. Application to model atoms and molecules
We propose and apply the finite-element discrete variable representation to
express the nonequilibrium Green's function for strongly inhomogeneous quantum
systems. This method is highly favorable against a general basis approach with
regard to numerical complexity, memory resources, and computation time. Its
flexibility also allows for an accurate representation of spatially extended
hamiltonians, and thus opens the way towards a direct solution of the two-time
Schwinger/Keldysh/Kadanoff-Baym equations on spatial grids, including e.g. the
description of highly excited states in atoms. As first benchmarks, we compute
and characterize, in Hartree-Fock and second Born approximation, the ground
states of the He atom, the H molecule and the LiH molecule in one spatial
dimension. Thereby, the ground-state/binding energies, densities and
bond-lengths are compared with the direct solution of the time-dependent
Schr\"odinger equation.Comment: 11 pages, 5 figures, submitted to Physical Review
Nonequilibrium Green function approach to photoionization processes in atoms
We present a quantum kinetic approach for the time-resolved description of
many-body effects in photoionization processes in atoms. The method is based on
the non-equilibrium Green functions formalism and solves the
Keldysh/Kadanoff-Baym equations in second Born approximation. An approximation
scheme is introduced and discussed, which provides a complete single-particle
description of the continuum, while the atom is treated fully correlated.Comment: 11 pages, 6 figure