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Determination of Elastic Moduli of NaCl by Brillouin Scattering (CAT#: STEM-ST-0091-YJL)

Introduction

The measurement of elastic constants as a function of pressure can provide valuable information not only for the understanding of atomic scale forces but for the interpretation of seismic data to better understand the nature of the Earth's interior. High pressures can be achieved by using a large force or by using a small area. The technique of laser Brillouin scattering is an ideal probe for measuring sound velocity in the small volume available in a gasketed diamond anvil cell.




Principle

From a quantum point of view, Brillouin scattering is an interaction of light photons with acoustic or vibrational quanta (phonons), with magnetic spin waves (magnons), or with other low frequency quasiparticles interacting with light. The interaction consists of an inelastic scattering process in which a phonon or magnon is either created (Stokes process) or annihilated (anti-Stokes process). The energy of the scattered light is slightly changed, that is decreased for a Stokes process and increased for an anti-Stokes process. This shift, known as the Brillouin shift, is equal to the energy of the interacting phonon and magnon and thus Brillouin scattering can be used to measure phonon and magnon energies.

Applications

Brillouin scattering is used to determine acoustic velocities and elastic properties of a number of crystalline solids, glasses, and liquids.

Procedure

1. Sample preparation
2. Measurement by scattering detection instrument
3. Data analysis

Materials

Brillouin scattering measurement system (Brillouin spectrometer)
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