Core-valence attosecond transient absorption spectroscopy of polyatomic molecules

TL;DR

This paper extends attosecond transient absorption spectroscopy (ATAS) theory to molecules, incorporating electron-nuclear dynamics, and demonstrates its ability to resolve ultrafast electron density changes with atomic resolution.

Contribution

It introduces a comprehensive theoretical framework for molecular ATAS that includes coupled electron-nuclear dynamics and applies it to observe charge oscillations in a polyatomic molecule.

Findings

ATAS can resolve electron density dynamics with atomic spatial resolution.

The extended theory accurately models coupled electron-nuclear processes in molecules.

Experimental application to propiolic acid reveals charge oscillations post-ionization.

Abstract

Tracing ultrafast processes induced by interaction of light with matter is often very challenging. In molecular systems, the initially created electronic coherence becomes damped by the slow nuclear rearrangement on a femtosecond timescale which makes real-time observations of electron dynamics in molecules particularly difficult. In this work, we report an extension of the theory underlying the attosecond transient absorption spectroscopy (ATAS) for the case of molecules, including a full account for the coupled electron-nuclear dynamics in the initially created wave packet, and apply it to probe the oscillations of the positive charge created after outer-valence ionization of the propiolic acid molecule. By taking advantage of element-specific core-to-valence transitions induced by X-ray radiation, we show that the resolution of ATAS makes it possible to trace the dynamics of electron density with atomic spatial resolution.