Wavenumber dependence of structural alpha relaxation in a molecular liquid

TL;DR

This study investigates how the structural alpha relaxation in liquid orthoterphenyl varies with wavenumber and temperature, revealing non-exponential behavior and correlations with static structure, consistent with mode coupling theory.

Contribution

It provides detailed experimental insights into the wavenumber dependence of alpha relaxation and its spectral shape variations in a molecular liquid.

Findings

Alpha relaxation amplitude and relaxation time vary with wavenumber.

Spectral line shape shows significant wavenumber dependence.

Alpha relaxation remains non-exponential even far above melting point.

Abstract

Structural alpha relaxation in liquid orthoterphenyl is studied by means of coherent neutron time-of-flight and backscattering spectroscopy over a large temperature range. Not only amplitude and relaxation time but also the spectral line shape show a significant variation with wavenumber. As expected from mode coupling theory, these variations are correlated with the static structure factor. Even far above the melting point, alpha relaxation remains non-exponential.