Laser Doppler Spectroscopy in an Oscillating Electric Field

Abstract

We investigate the photocurrent power spectrum induced by laser light scattered to a detector from a suspension of homogeneous charged particles in the presence of a square-wave electric field. Constraints associated with optimal heat dissipation require that a time-dependent field be used in order to obtain good resolution in measurements of electrophoretic mobilities. A calculation of the power spectrum yields an expression that depends on both the diffusion constant and electrophoretic mobility of the particle. This expression is used to analyze experimental data in order to obtain values for those parameters.