1,836 research outputs found
Time-dependent configuration-interaction-singles calculation of the -subshell two-photon ionization cross section in xenon
The two-photon ionization cross section of xenon in the photon-energy
range below the one-photon ionization threshold is calculated within the
time-dependent configuration-interaction-singles (TDCIS) method. The TDCIS
calculations are compared to random-phase-approximation (RPA) calculations
[Wendin \textit{et al.}, J. Opt. Soc. Am. B \textbf{4}, 833 (1987)] and are
found to reproduce the energy positions of the intermediate Rydberg states
reasonably well. The effect of interchannel coupling is also investigated and
found to change the cross section of the shell only slightly compared to
the intrachannel case.Comment: 11 pages, 3 figure
Strong-Field Many-Body Physics and the Giant Enhancement in the High-Harmonic Spectrum of Xenon
We resolve an open question about the origin of the giant enhancement in the
high-harmonic generation (HHG) spectrum of atomic xenon around 100 eV. By
solving the many-body time-dependent Schr\"odinger equation with all orbitals
in the 4d, 5s, and 5p shells active, we demonstrate the enhancement results
truly from collective many-body excitation induced by the returning
photoelectron via two-body interchannel interactions. Without the many-body
interactions, which promote a 4d electron into the 5p vacancy created by
strong-field ionization, no collective excitation and no enhancement in the HHG
spectrum exist.Comment: 5 pages, 4 figure
Imaging instantaneous electron flow with ultrafast resonant x-ray scattering
We propose a novel way to image dynamical properties of nonstationary
electron systems using ultrafast resonant x-ray scattering. Employing a
rigorous theoretical analysis within the framework of quantum electrodynamics,
we demonstrate that a single scattering pattern from a nonstationary electron
system encodes the instantaneous interatomic electron current in addition to
the structural information usually obtained by resonant x-ray scattering from
stationary systems. Thus, inelastic contributions that are indistinguishable
from elastic processes induced by a broadband probe pulse, instead of being a
concern, serve as an advantage for time-resolved resonant x-ray scattering.
Thereby, we propose an approach combining elastic and inelastic resonant x-ray
scattering for imaging dynamics of nonstationary electron systems in both real
space and real time. In order to illustrate its power, we show how it can be
applied to image the electron hole current in an ionized diatomic molecule
Driving Rabi oscillations at the giant dipole resonance in xenon
Free-electron lasers (FELs) produce short and very intense light pulses in
the XUV and x-ray regimes. We investigate the possibility to drive Rabi
oscillations in xenon with an intense FEL pulse by using the unusually large
dipole strength of the giant-dipole resonance (GDR). The GDR decays within less
than 30 as due to its position, which is above the ionization threshold.
We find that intensities around 10 W/cm are required to induce Rabi
oscillations with a period comparable to the lifetime. The pulse duration
should not exceed 100 as because xenon will be fully ionized within a few
lifetimes. Rabi oscillations reveal themselves also in the photoelectron
spectrum in form of Autler-Townes splittings extending over several tens of
electronvolt.Comment: 6 pages, 5 figure
Wave-packet propagation based calculation of above-threshold ionization in the x-ray regime
We investigate the multi-photon process of above-threshold ionization for the
light elements hydrogen, carbon, nitrogen and oxygen in the hard x-ray regime.
Numerical challenges are discussed and by comparing Hartree-Fock-Slater
calculations to configuration-interaction-singles results we justify the
mean-field potential approach in this regime. We present a theoretical
prediction of two-photon above-threshold-ionization cross sections for the
mentioned elements. Moreover, we study how the importance of above-threshold
ionization varies with intensity. We find that for carbon, at x-ray intensities
around , two-photon above-threshold ionization of the
K-shell electrons is as probable as one-photon ionization of the L-shell
electrons.Comment: 13 pages, 4 figures, 1 tabl
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