# Study of photoinduced valence dynamics in EuNi$_2$(Si$_{0.21}$Ge$_{0.79}$)$_2$ through time-resolved X-ray absorption spectroscopy

## TL;DR

This study uses time-resolved X-ray absorption spectroscopy to observe and analyze photoinduced valence transitions in EuNi$_2$(Si$_{0.21}$Ge$_{0.79}$)$_2$, revealing metastable states and electron dynamics.

## Contribution

It provides the first detailed experimental and theoretical analysis of photoinduced valence dynamics in this Eu-based compound.

## Key findings

- Observation of Eu$^{3+}$ to Eu$^{2+}$ valence transition
- Identification of a metastable state with up to 3 ns lifetime
- Quantitative evaluation of valence transition mechanisms

## Abstract

The photoinduced valence dynamics of EuNi$_2$(Si$_{0.21}$Ge$_{0.79}$)$_2$ are investigated using time-resolved X-ray absorption spectroscopy for Eu $M_5$-edge. Through the pump-probe technique with synchrotron X-ray and Ti:sapphire laser pulse, a photoinduced valence transition is observed from Eu$^{3+}$ to Eu$^{2+}$. Because the lifetime of a photoinduced state can be up to 3 ns, a metastable state is considered to be realized. By comparing the experimental results with the theoretical calculations, the photoinduced valence transition between Eu 4$f$ and conduction electrons is quantitatively evaluated.