Photon Correlation Techniques for Characterizing Small Fineparticles

Forty years ago anyone interested in fineparticle characterization who had a science degree could cope with the theory of the techniques and was able to build relatively simple equipment to carry out the measurements. In the two most recent areas of fineparticle characterization — diffractometers (discussed earlier) and the method to be discussed in this section photon correlation spectroscopy (PCS), the relevant theories involve the use of concepts normally not studied until the post graduate level in an honours physics degree. The theory also involves electronic equipment and data processing concepts out of reach for people without a mathematical background. For these instruments the expensive electronic processing equipment and size evaluation equipment can truly be called a black box, from the point of view of the average operator. 

When using the technique Finsey cautions that preparation of a suitable dispersion is sometimes difficult. Thus he states, 

Finsey states that if higher concentration involving multiple scattered light is used, 

One can also use fibre optics to measure Doppler shifted light in the back scattered mode to control polymerization processes in the production of latex spheres widely used in the coatings industry. Procedures are being developed to gain information by photon correlation spectroscopy using higher concentration suspensions. 

See instruction manual for fibre optic Doppler anemometer, published by SIRE (Scientific Instrument Research Establishment) Ltd., Southhill Chislehurst, Kent, England. W. H. Yanta, Measurement of Aerosol Size Distributions with a Laser Doppler Veloci-meter , National Bureau of Standards Special Publication 412, Aerosol Measurement, proceedings of a seminar on aerosol measurement held at National Bureau of Standards, Gaithersburg, Maryland, May 7, 1974. 

---

Photon Correlation Techniques for Characterizing Small Fineparticles 243... 

---