Multidimensional high-harmonic echo spectroscopy: resolving coherent electron dynamics in the EUV regime

TL;DR

This paper introduces a theoretical multidimensional high-harmonic echo spectroscopy method that uses strong optical fields to resolve ultrafast coherent electron dynamics in molecules within the EUV regime, achieving femtosecond resolution.

Contribution

It presents a novel semi-perturbative approach and demonstrates how high-harmonic echo signals can directly observe ultrafast valence electron dynamics with high temporal resolution.

Findings

Simulations show effective capture of ultrafast valence electron dynamics.

The method reveals nontrivial ultra-delayed partial rephasing echo.

Broad bandwidth of dipole transitions enables detailed energy resolution.

Abstract

We theoretically propose a multidimensional high-harmonic echo spectroscopy technique which utilizes strong optical fields to resolve coherent electron dynamics spanning an energy range of multiple electron Volts. Using our recently developed semi-perturbative approach, we can describe the coherent valence electron dynamics driven by a sequence of phase-matched and well separated short few-cycle strong infrared laser pulses. The recombination of tunnel-ionized electrons by each pulse coherently populates the valence states of a molecule, which allows for a direct observation of its dynamics via the high harmonic echo signal. The broad bandwidth of the effective dipole between valence states originated from the strong-field excitation results in nontrivial ultra-delayed partial rephasing echo, which is not observed in standard 2D optical spectroscopic techniques. We demonstrate the results of simulations for the anionic molecular system and show that the ultrafast valence electron dynamics can be well captured with femtosecond resolution.