Strong dependence of ultracold chemical rates on electric dipole moments

We use the quantum threshold laws combined with a classical capture model to provide an analytical estimate of the chemical quenching cross sections and rate coefficients of two colliding particles at ultralow temperatures. We apply this quantum threshold model (QT model) to indistinguishable fermionic polar molecules in an electric field. At ultracold temperatures and in weak electric fields, the cross sections and rate coefficients depend only weakly on the electric dipole moment d induced by the electric field. In stronger electric fields, the quenching processes scale as d{sup 4(L+(1/2))} where L>0 is the orbital angular-momentum quantum number between the two colliding particles. For p-wave collisions (L=1) of indistinguishable fermionic polar molecules at ultracold temperatures, the quenching rate thus scales as d{sup 6}. We also apply this model to pure two-dimensional collisions and find that chemical rates vanish as d{sup -4} for ultracold indistinguishable fermions. This model provides a quick and intuitive way to estimate chemical rate coefficients of reactions occuring with high probability.