Attosecond delays in molecular photoionization

TL;DR

This study measures and explains attosecond photoionization delays in N₂O and H₂O molecules, revealing large delays linked to shape resonances in N₂O and smaller delays in H₂O, advancing understanding of molecular electron dynamics.

Contribution

It introduces a combined experimental and theoretical approach to measure and interpret attosecond delays in molecular photoionization, highlighting the role of shape resonances.

Findings

Large delays up to 160 as in N₂O due to shape resonances

Smaller delays in H₂O below 50 as across 20-40 eV

Method enables detailed study of molecular attosecond dynamics

Abstract

We report measurements of energy-dependent attosecond photoionization delays between the two outer-most valence shells of N$_2$O and H$_2$O. The combination of single-shot signal referencing with the use of different metal foils to filter the attosecond pulse train enables us to extract delays from congested spectra. Remarkably large delays up to 160 as are observed in N$_2$O, whereas the delays in H$_2$O are all smaller than 50 as in the photon-energy range of 20-40 eV. These results are interpreted by developing a theory of molecular photoionization delays. The long delays measured in N$_2$O are shown to reflect the population of molecular shape resonances that trap the photoelectron for a duration of up to $\sim$110 as. The unstructured continua of H$_2$O result in much smaller delays at the same photon energies. Our experimental and theoretical methods make the study of molecular attosecond photoionization dynamics accessible.