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Study of Effect of Interparticle Interactions on the Diffusion Coefficient in Concentrated Magnetic Fluids by Forced Rayleigh Scattering (CAT#: STEM-ST-0064-YJL)

Introduction

The magnetic fluids are constituted of maghemite nanoparticles γ-Fe2O3 coated with citrate molecules that ensure them a negative superficial charge. They are dispersed in water at pH 7 with a volume fraction φ ranging from 1% up to 25%. The particle diameters d follow a lognormal distribution characterized here by d0=(<ln d>)=9.8 nm and σ=0.25. The dipolar parameter γ/φ =μ0m2V/KT that quantifies the dipolar interactions between two particles compared to thermal energy, is 32 for this ferrofluid.




Principle

Forced Rayleigh scattering (FRS) is a light scattering technique used to investigate light-induced grating structures that decay in a relaxational or almost relaxational manner. Such gratings can be created by interference and absorption of two pump beams and probed by a third beam, usually of different frequency. They may consist of spatially varying excited state populations with picosecond lifetimes or of long-lived variations in temperature, composition, and/or density. Forced Rayleigh scattering provides high sensitivity with respect to the amplitude and dynamics of such gratings and allows investigations not accessible by classical scattering techniques.

Applications

Forced Rayleigh Scattering is used to study fluid.

Procedure

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

Materials

Rayleigh scattering measurement system