This function will rotate a a 2nd rank spherical tensor using reduced Wigner rotations.
Chemical shift anisotropy is often described by a 2nd rank spherical tensor in the Principal Axis System(PAS):
R(2,m)(PAS)=sqrt(3/2)*aniso*[-sqrt(6)*eta/6 0 1 0 -sqrt(6)*eta/6]
This tensor will be described in the laboratory frame (LAB) by applying some wigner rotations, e.g.
The above could represent the following rotations
going from PAS coordinate system to LAB coordinate system via a MOL coordinate system.
source: Multidimensional Solid-State NMR and Polymers. Schmidt-Rohr & spiess. Academic press 1994