Simple treatment of ultracold polar molecule collisions

Collisions of polar molecules at ultracold ($< \mu K$) temperatures open the way for prospects of manipulating collision dynamics, including chemical reactions, by by varying an electric field. To understand such processes, one needs a scattering theory that accounts sufficiently accurately for the long-range van der Waals and dipolar forces acting between the molecules, but that also has a reasonable parametrization of the short-range physics when the molecules actually encounter one another. In this presentation we discuss a theory that marries a quantum-defect-theory parametrization of short-range physics \footnotemark[2], to a modified Langevin-like model that has successfully estimated the effect of electric fields \footnotemark[3]. We discuss the character of the resulting scattering, including field-dependent chemical reaction rates and resonances. \footnotetext[2]{Z. Idziaszek and P. S. Julienne, e-print arXiv:0912.0370 (2009).} \footnotetext[3]{ G. Qu\'{e}m\'{e}ner and J. L. Bohn, Phys. Rev. A, to appear (2009). }