Inelastic collisions of ultracold polar molecules

The collisional stability of ultracold polar molecules in electrostatic traps is considered. Rate constants for collisions that drive molecules from weak-electric-field-seeking to strong-field-seeking states are estimated using a simple model that emphasizes long-range dipolar forces. The rate constants for collisional losses are found to vary substantially as a function of molecular parameters used in the model, such as dipole moment, mass, and the splitting of the molecular $\Lambda$ doublet. Varying these parameters over physically reasonable ranges yields rate constants as low as ${10}^{-20}\hspace{0.5em}{\mathrm{cm}}^3/\sec$ and as high as ${10}^{-10}\hspace{0.5em}{\mathrm{cm}}^3/\sec .$ Nevertheless, the loss rates rise dramatically in the presence of the externally applied trapping electric field. For this reason it is argued that electrostatic traps are likely to be less stable against collisional losses than their magnetic counterparts.