Abstract
A variety of processes originating from the interaction of atomic or molecular N-electron states with strong and/or hypershort radiation pulses can be understood quantitatively only by first determining with good accuracy the solutions of the many-electron time-dependent Schrödinger equation (METDSE) that describe the corresponding physics. The METDSE is solvable nonperturbatively via the state-specific expansion approach (SSEA). SSEA solutions have been used, or can be used, for quantitative explanation and numerically reliable predictions of quantities that have been measured or are measurable in modern laser-driven experiments that can track, with hypershort (attosecond) time resolution, the effects of electron rearrangements in atoms and molecules. The calculations take into account in a transparent way the interplay between the phenomena and the electronic structures of the physically significant states in discrete and multichannel continuous spectra, including multiply- and inner-hole–excited resonance states. The discussion focuses on novel topics of time-resolved many-electron physics and includes a comparison of our predictions to recent quantitative measurements of attosecond-resolved generation of the profile of the ( 2 s 2 p ) 1 P o doubly excited resonance state of helium during photoionization and of the relative time delay in photoemission of the (2s,2p) electrons of neon.
Highlights
PrologueThe paper was written in response to an invitation by the editor (M. Schultze) to contribute a brief account of theoretical work and corresponding results that my colleagues Komninos and Mercouris and I have produced since the 1990s on topics that were announced for this special issue
In modern studies of the interaction of hypershort and/or strong radiation pulses for a large range of wavelengths with atoms and molecules, a desideratum of crucial importance is the possibility of extracting quantitative information and understanding about nonlinear processes for different wavelengths, or time-resolved phenomena of hyperfast electron dynamics, where both the discrete spectrum and the multichannel continua, including resonance electronic states, are involved.As regards theory, such information and understanding can become accessible via formal constructions and computational methods that can go beyond the level of phenomenology or one-electron models and solve a variety of time-dependent many-electron problems (TDMEPs) on the time axis
In order to explore the prospects of practical spectroscopic use of attosecond pulses for issues of time-resolved effects of electron dynamics on spectra, we identified as suitable candidates the doubly excited states (DESs) in the continuous spectrum of helium [1,2,3,14,15]
Summary
The paper was written in response to an invitation by the editor (M. Schultze) to contribute a brief account of theoretical work and corresponding results that my colleagues Komninos and Mercouris and I have produced since the 1990s on topics that were announced for this special issue. The following discussion aims at doing just that, by commenting briefly on certain of our proposals, computational tools, and numerical results on themes concerning electron dynamics in many-electron atoms and molecules that can be studied, theoretically and experimentally, with attosecond resolution. Solving such past and future prototypical problems involves calculating and using the many-electron, time-dependent wavefunction,Ψ(t), describing the physics of interest. The SSEA and the theory of electronic structures on which it is based provide the conceptual and practical framework for quantitatively treating time-dependent many-electron problems (TDMEPs) [1,2,3], such as those resulting from the interaction of atoms and molecules with femtosecond and attosecond pulses and have to do with hyperfast electronic processes
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