Efficient method for quantum calculations of molecule-molecule scattering properties in a magnetic field

We show that the cross sections for molecule-molecule collisions in the presence of an external field can be computed efficiently using a total angular momentum basis, defined either in the body-fixed frame or in the space-fixed coordinate system. This method allows for computations with much larger basis sets than previously possible. We present calculations for (NH)-N-15-(NH)-N-15 collisions in a magnetic field. Our results support the conclusion of the previous study that the evaporative cooling of rotationally ground (NH)-N-15 molecules in a magnetic trap has a prospect of success. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733288]