# Two-photon resonant excitation of interatomic coulombic decay in neon dimers

## TL;DR

This paper demonstrates the first observation of two-photon resonant excitation of interatomic Coulombic decay in neon dimers using free electron laser pulses, combining experimental results with theoretical calculations.

## Contribution

It reports the experimental observation of two-photon resonant ICD in neon dimers enabled by tunable EUV pulses, supported by ab initio theoretical analysis.

## Key findings

- Resonant two-photon excitation of ICD observed in neon dimers.
- Clear signature of ICD mechanism in ion yield ratios.
- Theoretical calculations support experimental results.

## Abstract

The recent availability of intense and ultrashort extreme ultraviolet sources opens the possibility to investigate ultrafast electronic relaxation processes in matter in an unprecedented regime. In this work we report on the observation of two-photon excitation of interatomic Coulombic decay (ICD) in neon dimers using the tunable intense pulses delivered by the free electron laser FERMI@Elettra. The unique characteristics of FERMI (narrow bandwidth, spectral stability, and tunability) allow one to resonantly excite specific ionization pathways and to observe a clear signature of the ICD mechanism in the ratio of the ion yield created by Coulomb explosion. The present experimental results are explained by \emph{ab initio} electronic structure and nuclear dynamics calculations.