Quantitative rescattering theory for laser-induced high-energy plateau photoelectron spectra

Abstract

A comprehensive quantitative rescattering (QRS) theory for describing the production of highenergy photoelectrons generated by intense laser pulses is presented. According to the QRS, the momentum distributions of these electrons can be expressed as the product of a returning electron wave packet with the elastic differential cross sections (DCS) between free electrons with the target ion. We show that the returning electron wave packets are determined mostly by the lasers only, and can be obtained from the strong field approximation. The validity of the QRS model is carefully examined by checking against accurate results from the solution of the time-dependent Schrödinger equation for atomic targets within the single active electron approximation. We further show that experimental photoelectron spectra for a wide range of laser intensity and wavelength can be explained by the QRS theory, and that the DCS between electrons and target ions can be extracted from experimental photoelectron spectra. By generalizing the QRS theory to molecular targets, we discuss how few-cycle infrared lasers offer a promising tool for dynamic chemical imaging with temporal resolution of a few femtoseconds.

Laser-Induced Electron Diffraction for Probing Rare Gas Atoms

“…The viability of this self-imaging technique, dubbed laser-induced electron diffraction (LIED), has been addressed by several theoretical [6][7][8][9] and experimental [10,11] studies. A key principle was established by the quantitative rescattering (QRS) theory [7]: the field-free large-angle electron-ion (e-ion) elastic differential cross section (DCS) can be retrieved from a measured HATI electron momentum distribution. However in order for LIED to become an effective ultrafast imaging method, it is necessary that the valence (outer-shell) electrons of the target, e.g., molecules, play no significant role in the elastic process since their rearrangement which induces structural dynamics, i.e., motion of nuclei, is de facto unknown, and thus their interaction with the recolliding electron cannot be characterized.…”

“…The combined elements of elastic scattering occurring on an optical-cycle time scale, e.g., femtoseconds, inherent in this model has generated interest in exploiting this as an ultrafast structural probe [3], analogous to diffraction using electron beams [4,5]. The viability of this self-imaging technique, dubbed laser-induced electron diffraction (LIED), has been addressed by several theoretical [6][7][8][9] and experimental [10,11] studies. A key principle was established by the quantitative rescattering (QRS) theory [7]: the field-free large-angle electron-ion (e-ion) elastic differential cross section (DCS) can be retrieved from a measured HATI electron momentum distribution.…”

Diffraction using laser-driven broadband electron wave packets

“…First, the atom's plateau is enhanced compared with its molecular counterpart. In accordance to the quantitative rescattering theory 40 , the detected electron yield can be expressed as a product of electron's RWP and the field-free DCS. In Supplementary Fig.…”

“…We first follow the quantitative rescattering theory 40 to extract the collision-energy-dependent molecular DCS of nitrogen from the photoelectron energy distribution; the background signal, that is, atomic scattering DCS and electron RWP, is then removed, leaving only the oscillating interference fringes. The electron RWP distribution W(|k r |), defined as D(k)/s(k r ) in the quantitative rescattering theory, is obtained from the photoelectron spectrum of argon under identical laser conditions.…”

“…This behaviour is universal even for large molecules. Second, strong-field experimental and theoretical studies 31,[40][41][42] have shown that the returning broadband wave packet (RWP) energy distribution is also a smooth continuous function, further facilitating extraction.…”