Dynamic Light Scattering

Brookhaven Instruments Corp.,

  • Particles suspended in a liquid are subject to Brownian motion.
  • Small particles diffuse"faster".
  • Large particles diffuse "slower".
  • The time variation of the scattered intensity is analyzed by examining their auto-correlation. From this a diffusion coefficient can be derived. Please see our literature section for additional infornmation.
  • From the measured diffusion coefficient particle size is calculated.
    • A beam of laser light is focussed in the sample.
    • Particles in the scattering volume scatter light in all directions.
    • The scattered photons are measured by a photomultiplier tube
    • The Intensity appears to fluctuate randomly.
    • A digital correlator is used to compute the autocorrelation function.

    • The autocorrelation function is an exponential decay:

    • Each monodisperse population of particle sizes produces its own unique autocorrelation function - a single exponential decay.
    • Mixtures of more than one size population produce sums of exponentials.
    • Available algorithms can be used to extract "true" size distributions from complex samples - NNLS, CONTIN.

    With kind permission of Brookhaven Instruments Corp.