Pre-equilibrium stopping and charge capture in proton-irradiated aluminum sheets

TL;DR

This study uses first-principles calculations to analyze how protons lose energy and capture charge in thin aluminum sheets, revealing enhanced stopping power near the surface and introducing a new method to determine the projectile's charge state after transmission.

Contribution

It provides the first detailed theoretical analysis of pre-equilibrium stopping and charge capture in thin aluminum, highlighting surface plasma oscillations as a key factor and developing a novel orbital-resolved charge state computation method.

Findings

Enhanced stopping power near the surface layers.

Surface plasma oscillations as a key excitation channel.

New technique for orbital-resolved charge state calculation.

Abstract

We present a first-principles study of pre-equilibrium stopping power and projectile charge capture in thin aluminum sheets irradiated by 6 - 60 keV protons. Our time-dependent density functional theory calculations reveal enhanced stopping power compared to bulk aluminum, particularly near the entrance layers. We propose the additional excitation channel of surface plasma oscillations as the most plausible explanation for this behavior. We also introduce a novel technique to compute the orbital-resolved charge state of a proton projectile after transmission through the sheet. Our results provide insight into the dynamics of orbital occupations after the projectile exits the aluminum sheet and have important implications for advancing radiation hardness and focused-ion beam techniques, especially for few-layer materials.