Nonlinear optical tagging diagnostic for the measurement of Fokker-Planck diffusion and electric fields

Strong optical pumping of ions can result after a few microseconds of reson ance excitation in a laser beam. However, both Fokker-Planck diffusion and acceleration due to macroscopic electric fields can remove an ion from reso nance by changing the ion velocity on a similar timescale. Therefore, the t ime dependence of laser induced fluorescence can be influenced by particle acceleration and velocity-space diffusion. This effect which has already be en used to measured Fokker-Planck diffusion, is extended to include the inf luence of an electric field and used to measure the electric field associat ed with an electrostatic shock in a multipolar gas discharge. (C) 2001 Amer ican Institute of Physics.