# Electronic Stopping of Slow Protons in Transition and Rare Earth Metals: Breakdown of the Free Electron Gas Concept

## TL;DR

This study investigates how slow protons lose energy in transition and rare earth metals, revealing that traditional free electron models fail to explain the high electronic stopping cross sections observed in Ta and Gd.

## Contribution

It provides experimental measurements of electronic stopping cross sections in Ta and Gd and demonstrates the breakdown of the free electron gas model for these materials.

## Key findings

- High SCS in Ta and Gd cannot be explained by free electron gas model.
- Electronic stopping correlates with densities of electronic states in the metals.
- Experimental data highlight limitations of simple models for complex metals.

## Abstract

The electronic stopping cross sections (SCS) of Ta and Gd for slow protons have been investigated experimentally. The data are compared to the results for Pt and Au to learn how electronic stopping in transition and rare earth metals correlates with features of the electronic band structures. The extraordinarily high SCS observed for protons in Ta and Gd cannot be understood in terms of a free electron gas model, but are related to the high densities of both occupied and unoccupied electronic states in these metals.

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Source: https://tomesphere.com/paper/1703.03171