Collisions of cold polar molecules in a microwave cavity

We present accurate quantum calculations for low-temperature collisions of polar molecules and atoms in a microwave laser field. The effects of the radiation field on the collision dynamics are described exactly using the dressed-state formalism of quantum optics. Our calculations identify new mechanisms for rotational relaxation of molecules placed in a microwave cavity and indicate that molecular collisions at temperatures below 0.5 K can be efficiently manipulated with microwave laser fields of moderate strength.