POLARIZATION DEPENDENCE OF OPTICAL SUPPRESSION IN PHOTOASSOCIATIVE IONIZATION COLLISIONS IN A SODIUM MAGNETOOPTIC TRAP

Three-dimensional quantum scattering calculations predict that the deg ree of optical shielding of cold collisions saturates with increasing intensity very differently from two-state models and is sensitive to t he polarization of the shielding light. We report measurements showing how suppression of Na photoassociative ionization (PAI) rates is sens itive to the intensity and polarization of the shielding laser. At hig her intensities, circular polarization suppresses PAI rates an order o f magnitude more effectively than linear polarization, in qualitative agreement with our model calculations.