24 research outputs found
In-plane Theory of Non-Sequential Triple Ionization
We describe first-principles in-plane calculations of non-sequential triple
ionization (NSTI) of atoms in a linearly polarized intense laser pulse. In a
fully classically correlated description, all three electrons respond
dynamically to the nuclear attraction, the pairwise e-e repulsions and the
laser force throughout the duration of a 780nm laser pulse. Nonsequential
ejection is shown to occur in a multi-electron, possibly multi-cycle and
multi-dimensional, rescattering sequence that is coordinated by a number of
sharp transverse recollimation impacts.Comment: 4 pages, 4 figure
Non-Sequential Double Ionization is a Completely Classical Photoelectric Effect
We introduce a unified and simplified theory of atomic double ionization. Our
results show that at high laser intensities ( watts/cm)
purely classical correlation is strong enough to account for all of the main
features observed in experiments to date
Momentum Analysis in Strong-field Double Ionization
We provide a basis for the laser intensity dependence of the momentum
distributions of electrons and ions arising from strong-field non-sequential
double ionization (NSDI) at intensities in the range . To do this we use a completely classical method introduced previously
\cite{ho-etal05}. Our calculated results reproduce the features of experimental
observations at different laser intensities and depend on just two distinct
categories of electon trajectories.Comment: 5 pages, 7 figure
Classical Effects of Laser Pulse Duration on Strong-field Double Ionization
We use classical electron ensembles and the aligned-electron approximation to
examine the effect of laser pulse duration on the dynamics of strong-field
double ionization. We cover the range of intensities
for the laser wavelength 780 nm. The classical scenario suggests that the
highest rate of recollision occurs early in the pulse and promotes double
ionization production in few-cycle pulses. In addition, the purely classical
ensemble calculation predicts an exponentially decreasing recollision rate with
each subsequent half cycle. We confirm the exponential behavior by trajectory
back-analysis
Resonant propagation of x rays from the linear to the nonlinear regime
We present a theoretical study of temporal, spectral, and spatial reshaping of intense, ultrafast x-ray pulses propagating through a resonant medium. Our calculations are based on the solution of a three-dimensional time-dependent Schrödinger-Maxwell equation, with the incident x-ray photon energy on resonance with the core-level 1s-3p transition in neon. We study the evolution of the combined incident and medium-generated field, including the effects of stimulated emission, absorption, ionization, and Auger decay, as a function of the input pulse energy and duration. We find that stimulated Raman scattering between core-excited states 1s-13p and 2p-13p occurs at high x-ray intensity, and that the emission around this frequency is strongly enhanced when also including the similar 1s-1-2p-1 response of the ion. We also explore the dependence of x-ray self-induced transparency (SIT) and self-focusing on the pulse intensity and duration, and we find that the stimulated Raman scattering plays an important role in both effects. Finally, we discuss how these nonlinear effects may potentially be exploited as control parameters for pulse properties of x-ray free-electron laser sources
Atomistic three-dimensional coherent x-ray imaging of nonbiological systems
We computationally study the resolution limits for three-dimensional coherent x-ray diffractive imaging of
heavy, nonbiological systems using Ar clusters as a prototype. We treat electronic and nuclear dynamics on an
equal footing and remove the frozen-lattice approximation often used in electronic damage studies. We explore
the achievable resolution as a function of pulse parameters (fluence level, pulse duration, and photon energy) and
particle size. The contribution of combined lattice and electron dynamics is not negligible even for 2 fs pulses,
and the Compton scattering is less deleterious than in biological systems for atomic-scale imaging. Although
free-electron scattering represents a significant background, we find that recovery of the original structure is in
principle possible with 3 °A resolution for particles of 11 nm diameter