Ultracold NH-NH collisions in magnetic fields

The production of cold and ultracold molecules opens up the possibility to control chemical reactions by means of electromagnetic fields. The NH ($^3\Sigma^-$) molecule is a promising candidate for cold controlled chemistry, due to its large electric and magnetic dipole moment. We constructed high level, {\em ab initio}, singlet, triplet, and quintet interaction potentials, with analytic longe expansions for the entrance channel for chemical reaction [1]. We present preliminary quantum scattering calculations of the elastic and Zeeman relaxation cross sections from the cold (1K) down to the ultracold ($10^{-8}$ K) regime in magnetic fields ranging from $10^{-4}$ to $10^4$ gauss. We also investigate the effect of the intra- and inter-molecular spin-spin interactions. A large number of resonances over many orders of magnitude are found in elastic and inelastic cross sections. \\[4pt] [1] Liesbeth M. C. Janssen, Gerrit C. Groenenboom, Ad van der Avoird, Piotr S.~\.{Z}uchowski, and Rafa{\l} Podeszwa, J. Chem. Phys. {\bf 131}, 224314 (2009).