Laser Doppler Velocimetry
- Laser beams are aligned at the stationary layer in the cell
- At the crossing point of the beams, Young's interference fringes of known spacing are formed
- Particles moving through the fringes under the influence of the applied electric field scatter light whose intensity fluctuates with a frequency that is related to the particles velocity
- Photons detected are input to a digital correlator
- A frequency spectrum is produced from which the mobility and hence zeta potential are calculated
What about particles with no charge?
What happens if the fringes move but the particles do not?
- Particles with no charge will not move in an applied electric field
- They will not be able to be detected
- This problem is overcome by making the interference fringes move
- This is done by using a device called a modulator
What happens if the fringes and the particles are moving?
Return to "Defintion of Terms"