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Article
On the quantum field theory of photoionisation and electron scattering reactions on atoms
Brillouin-Wigner perturbation theory, formulated in the Schrödinger picture of quantum field theory, is employed to derive a perturbative scheme for the scattering matrix for photoionisation and electron scatt...
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Article
Strong laser fields interacting with matter I
We discuss non-perturbative aspects of the Floquet picture for the interaction of single mode strong laser fields with electrons. In numerical studies we show that this system stays adiabatic to a surprising d...
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Article
The role of avoided crossings in the dynamics of strong laser field — matter interactions
The structure of quasi-energy surfaces, i.e. of quasi-energies as functions of external parameters like the laser frequency, laser intensity, atomic distances etc., is discussed and avoided crossings are trace...
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Article
Adiabatic processes in the ionization of highly excited hydrogen atoms
Adiabatic and non-adiabatic processes in the dynamics of periodically driven quantum systems are studied employing the Floquet picture of quantum mechanics. The validity ofN-niveau approximations in the Floquet t...
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Article
Adiabatic motion and the structure of quasi-energy surfaces of periodically driven quantum systems
General repercussions of the extraordinarily rich avoidedcrossing structure in the parametric dependence of quasi-energies are discussed. A coarse-graining procedure leading to smooth effective quasienergy sur...
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Article
Highly excited hydrogen atoms in strong microwave fields
Employing a (1+1)-dimensional model, we discuss non-perturbative methods for the description of the ionization of highly excited hydrogen atoms by a pulsed strong microwave field. We restrict our attention to ...
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Article
The quantum theory of an ideal superlattice responding to far-infrared laser radiation
Minibands of quasienergies can be defined for a superlattice interacting with far-infrared laser radiation. It is demonstrated that the width of these quasienergy minibands depends not only on the parameters o...
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Article
Perturbative and nonperturbative processes in adiabatic population transfer
With the help of superadiabatic techniques for quantum systems depending slowly on time, we demonstrate how the total transition amplitude, tracked in time in the usual adiabatic basis, can be decomposed into ...
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Article
Floquet theory for short laser pulses
We develop adiabatic perturbation theory for quantum systems responding to short laser pulses, with or without a frequency chirp. Our approach rests on lifting the time-dependent Schrödinger equation to an ext...
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Article
Coherent control of the self-trap** transition
We discuss the dynamics of two weakly coupled Bose-Einstein condensates in a double-well potential, contrasting the mean-field picture to the exact N-particle evolution. On the mean-field level, a self-trap** t...
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Article
Thermal radiation and near-field energy density of thin metallic films
We study the properties of thermal radiation emitted by a thin dielectric slab, employing the framework of macroscopic fluctuational electrodynamics. Particular emphasis is given to the analytical construct...
