Intracycle interference in ionization of Ar by a laser assisted XUV pulse

Synopsis We present a theoretical and experimental study of the subcycle interference in laser assisted XUV ionization of Ar atoms. Averaging over the focal volume happens to blur the intracycle interference, which thus cannot be measured directly. We show that even at these conditions, the intracycle interference can be obtained through the subtraction of two different angle and energy-resolved distributions at slightly different laser intensities

Optimized time-dependent perturbation theory for pulse-driven quantum dynamics in atomic or molecular systems

We present a time-dependent perturbative approach adapted to the treatment of intense pulsed interactions. We show there is a freedom in choosing secular terms and use it to optimize the accuracy of the approximation. We apply this formulation to a unitary superconvergent technique and improve the accuracy by several orders of magnitude with respect to the Magnus expansion.Comment: 4 pages, 2 figure

Modelling laser-atom interactions in the strong field regime

We consider the ionisation of atomic hydrogen by a strong infrared field. We extend and study in more depth an existing semi-analytical model. Starting from the time-dependent Schroedinger equation in momentum space and in the velocity gauge we substitute the kernel of the non-local Coulomb potential by a sum of N separable potentials, each of them supporting one hydrogen bound state. This leads to a set of N coupled one-dimensional linear Volterra integral equations to solve. We analyze the gauge problem for the model, the different ways of generating the separable potentials and establish a clear link with the strong field approximation which turns out to be a limiting case of the present model. We calculate electron energy spectra as well as the time evolution of electron wave packets in momentum space. We compare and discuss the results obtained with the model and with the strong field approximation and examine in this context, the role of excited states.Comment: 11 pages, 5 figure

Efficient and accurate modeling of electron photoemission in nanostructures with TDDFT

We derive and extend the time-dependent surface-flux method introduced in [L. Tao, A. Scrinzi, New J. Phys. 14, 013021 (2012)] within a time-dependent density-functional theory (TDDFT) formalism and use it to calculate photoelectron spectra and angular distributions of atoms and molecules when excited by laser pulses. We present other, existing computational TDDFT methods that are suitable for the calculation of electron emission in compact spatial regions, and compare their results. We illustrate the performance of the new method by simulating strong-field ionization of C60 fullerene and discuss final state effects in the orbital reconstruction of planar organic molecules

Doubly-differential intracycle interference in above threshold photoionization

We analyze the doubly-differential momentum distributions of electrons ejected at the interaction of strong IR laser pulses with atoms. With the help of a semiclassical model we clarify the interplay between intracycle and intercycle interferences. The model results are compared with numerical solutions of the time-dependent Schrödinger equation for atoms with long-range potentials. Similarities and differences will be discussed. © Published under licence by IOP Publishing Ltd.Fil:Arbó, D.G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Doubly-differential intracycle interference in above threshold photoionization

We analyze the doubly-differential momentum distributions of electrons ejected at the interaction of strong IR laser pulses with atoms. With the help of a semiclassical model we clarify the interplay between intracycle and intercycle interferences. The model results are compared with numerical solutions of the time-dependent Schrödinger equation for atoms with long-range potentials. Similarities and differences will be discussed. © Published under licence by IOP Publishing Ltd.Fil:Arbó, D.G. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Non-perturbative semiclassical model for strong-field ionization

Synopsis We present a non-perturbative semiclassical model for strong-field ionization that accounts for path interferences of tunnel-ionized electrons in the ionic potential within the framework of a classical trajectory Monte-Carlo representation of the phase-space dynamics