Birefringence due to free electrophoresis

We calculate the steady-state birefringence and dichroism for the case of a rigid bent rod molecule due to the free electrophoresis. In order to find the orientational distribution function, we use the Fokker–Planck equation and solve it by the perturbation method (for the steady state) at low electric field. We find that, using convenient parameters to characterize the DNA solution, both, the calculated electric birefringence and the dichroism, for low electric fields, have positive values in concordance with the experimental results.