Polarization dependence of optical suppression in sodium

Summary form only given. The use of a cold beam of sodium allows us to probe the angular dependence of the linear polarization case. We have measured the decrease in the ionizing collision rate by monitoring the fractional decrease in photoassociative ionisation (PAI) in a Zeeman-slowed sodium beam. We see that the suppression with light polarized perpendicular to the atomic beam is greater than that with parallel. Increased suppression is observed with increasing intensity of the light.