Fingerprints of hydrogen bonding in the terahertz dynamics of ethanol and water: an Inelastic X-Ray Scattering study

We used Inelastic X-Ray Scattering methods to measure the terahertz spectrum of density fluctuations of ethanol inboth liquid and solid phases. The results of a Bayesian inference-based lineshape analysis with a multiple excitationmodel and the comparison with a previous similar analysis on water indicate that the different structures induced byhydrogen bonds in ethanol and water have a profound influence on the respective dynamic responses, the latter beingcharacterized by longer living and better resolved high-frequency acoustic excitations. Also, we compare these findingswith those obtained with an alternative approach based on the Exponential Expansion Theory and ensuring sum rulefulfillment, demonstrating that the model's choice directly impacts the number of spectral modes detected.