Multidimensional high harmonic spectroscopy: A semi-classical perspective on measuring multielectron rearrangement upon ionization

TL;DR

This paper proposes a multidimensional high harmonic spectroscopy technique that separates ionization and recombination dynamics in molecules, enabling detailed analysis of multielectron rearrangements with improved resolution and simplicity.

Contribution

It introduces a multidimensional approach extending previous 2D methods, allowing independent characterization of ionization delays and rates in high harmonic spectroscopy.

Findings

Enables separate measurement of ionization and recombination dynamics.

Extends 2D spectroscopy capabilities with a simpler reconstruction process.

Uses orthogonally polarized strong and multicolour control fields for optimization.

Abstract

High harmonic spectroscopy has the potential to combine attosecond temporal with sub-Angstrom spatial resolution of the early nuclear and multielectron dynamics in molecules. It involves strong field ionization of the molecule by the IR laser field followed by time-delayed recombination of the removed electron with the molecular ion. The time-delay is controlled on the attosecond time scale by the oscillation of the IR field and is mapped into the harmonic number, providing a movie of molecular dynamics between ionization and recombination. One of the challenges in the analysis of high harmonic signal stems from the fact that the complex dynamics of both ionization and recombination with their multiple observables are entangled in the harmonic signal. Disentangling this information requires multidimensional approach, capable of mapping ionization and recombination dynamics into different independent parameters. We suggest multidimensional high harmonic spectroscopy as a tool for characterizing of ionization and recombination processes separately allowing for simultaneous detection of both the ionization delays and sub-cycle ionization rates. Our method extends the capability of the two dimensional (2D) set-up suggested recently by Shafir et al on reconstructing ionization delays, while keeping the reconstruction procedure as simple as in the original proposal. The scheme is based on the optimization of the high harmonic signal in orthogonally polarized strong fundamental and relatively weak multicolour control fields.