Instrumentation

Basic Components: - Laser Source: A coherent light source, typically a He-Ne laser or a diode laser, with a specific wavelength (e.g., 633 nm). - Sample Holder: Usually a cuvette made of quartz or glass, which holds the sample solution. - Detector: A photomultiplier tube (PMT) or an avalanche photodiode (APD) detects the scattered light. - Autocorrelator: A digital device that computes the time correlation of the scattered light intensity.

Photon Correlation Spectroscopy (PCS): - PCS measures the time fluctuations of scattered light intensity. The autocorrelation function is analyzed to obtain the diffusion coefficient and particle size distribution. - PCS is sensitive to particles ranging from a few nanometers to several micrometers.

Depolarized Fabry-Perot Interferometry (FPI): - FPI measures the frequency broadening of scattered light due to rotational diffusion of anisotropic particles. It provides information about particle shape and dimensions.

Measurement Configurations: - Backscatter Detection (173°): Enhances sensitivity for small particles by increasing the detected count rate. It is particularly useful for measuring particles at low concentrations.

• Figure: A detailed diagram showing the laser source, sample holder, detector, and autocorrelator setup. Include labels and brief descriptions of each component.