Inelastic neutron scattering due to acoustic vibrations confined in nanoparticles: theory and experiment

TL;DR

This paper combines theoretical calculations and experimental measurements to study inelastic neutron scattering caused by acoustic vibrations confined in nanoparticles, highlighting factors that enable observation of these vibrational modes.

Contribution

It presents a theoretical framework for inelastic neutron scattering in nanoparticles and reports experimental data on TiO2 nanoparticles, identifying key factors for observing confined vibrational modes.

Findings

Theoretical calculations of neutron scattering due to confined acoustic vibrations.

Experimental inelastic neutron scattering data for TiO2 nanoparticles.

Identification of factors like size distribution and surface hydrogen that enhance vibrational mode detection.

Abstract

The inelastic scattering of neutrons by nanoparticles due to acoustic vibrational modes (energy below 10 meV) confined in nanoparticles is calculated using the Zemach-Glauber formalism. Such vibrational modes are commonly observed by light scattering techniques (Brillouin or low-frequency Raman scattering). We also report high resolution inelastic neutron scattering measurements for anatase TiO2 nanoparticles in a loose powder. Factors enabling the observation of such vibrations are discussed. These include a narrow nanoparticle size distribution which minimizes inhomogeneous broadening of the spectrum and the presence of hydrogen atoms oscillating with the nanoparticle surfaces which enhances the number of scattered neutrons.