Towards a theory of attosecond transient recorder

TL;DR

This paper develops a quantum-mechanical model for laser-assisted photoemission with chirped XUV pulses, analyzing streaked spectra and proposing a more accurate initial distribution for interpreting attosecond transient recordings.

Contribution

It introduces an exactly solvable model and a new ansatz for initial electron distributions, improving the understanding of streaked spectra in attosecond photoemission.

Findings

The classical model effectively maps initial distributions to final energies.

The actual initial distribution differs from the one without the probe laser.

Limitations of semiclassical theory are identified for long chirped pulses.

Abstract

Laser assisted photoemission by a chirped subfemtosecond extreme ultraviolet (XUV) pulse is considered within an exactly solvable quantum-mechanical model. Special emphasis is given to the energy dependence of photoexcitation cross-section. The streaked spectra are analyzed within the classical picture of initial time-momentum distribution r_ini(p,t) of photoelectrons mapped to the final energy scale. The actual time-momentum distribution in the absence of the probe laser field is shown to be a poor choice for r_ini, and a more adequate ansatz is suggested. The semiclassical theory offers a simple practically useful approximation for streaked spectra. Its limitations for sufficiently long chirped XUV pulses are established.