# Ultrafast dynamics in core-excited states probed by resonant Auger spectroscopy: pyrrole

## TL;DR

This paper uses resonant Auger spectroscopy to study ultrafast molecular changes in pyrrole after core excitation.

## Contribution

The study demonstrates resonant Auger spectroscopy's ability to probe out-of-plane nuclear motions and electronic structure in core-excited states.

## Key findings

- Resonant Auger spectroscopy captures ultrafast nuclear motions during core-hole relaxation.
- The technique reveals electronic structure details not accessible via X-ray absorption or photoelectron spectroscopy.
- It can resolve near-degenerate electronic transitions unresolved in X-ray absorption spectra.

## Abstract

We present high-resolution resonant Auger spectra of pyrrole at both the nitrogen and carbon edges. Through comparison to high-level quantum chemical calculations and a linear vibronic coupling model, we show how resonant Auger spectroscopy can capture the out-of-plane nuclear motions that occur during the few femtosecond core–hole relaxation processes. We also demonstrate how, in scenarios where there are near-degenerate electronic transitions in the X-ray absorption spectrum that cannot be resolved experimentally, resonant Auger can be used as a probe of the underlying electronic structure. Overall, resonant Auger is a technique capable of revealing detailed information about core-excited molecules that cannot be recovered through X-ray absorption or photoelectron spectroscopy alone.

High-resolution resonant Auger spectra of pyrrole at the carbon edge reveals information on ultrafast dynamics in the core-excited states.