  We examine the quenching reaction Rb (doublet S) + NH (singlet Delta) goes to
Rb (doublet P one-half) + NH (ground triplet Sigma minus). This reaction may be
utilized to produce ground state NH molecules for studies of ultracold physics
or for other purposes, and is interesting in that it involves initial and final
states that are nearly degenerate. This near degeneracy is expected to lead to
a large reaction rate. We examine this system using ab initio quantum chemistry
calculations and scattering calculations, which include spin-orbit effects, and
find that the reaction rate is large and, in fact, approaches the quantum
mechanical unitarity limit. We discuss the prospects for an experimental
examination of this system.
