Ab-initio simulations and measurements of the free-free opacity in Aluminum

TL;DR

This paper demonstrates how to model free-free opacity in aluminum using time-dependent density functional theory, incorporating corrections, and validates the approach with experimental data across various regimes.

Contribution

The study introduces a method to calculate free-free opacity in dense aluminum at finite temperatures using TDDFT, including local field, core polarization, and self-energy corrections.

Findings

Good agreement with experimental measurements across x-ray to UV wavelengths.

Accurate modeling of free-free opacity in warm-dense aluminum regimes.

Validation against plasma models at temperatures above 10 eV.

Abstract

The free-free opacity in dense systems is a property that both tests our fundamental understanding of correlated many-body systems, and is needed to understand the radiative properties of high energy-density plasmas. Despite its importance, predictive calculations of the free-free opacity remain challenging even in the condensed matter phase for simple metals. Here we show how the free-free opacity can be modelled at finite-temperatures via time-dependent density functional theory, and illustrate the importance of including local field corrections, core polarization and self-energy corrections. Our calculations for ground-state Al are shown to agree well with experimental opacity measurements performed on the Artemis laser facility across a wide range of x-ray to ultraviolet wavelengths. We extend our calculations across the melt to the warm-dense matter regime, and find good agreement with advanced plasma models based on inverse bremsstrahlung at temperatures above 10 eV.