This is the Trott, Abergel and Palmer 2003 R1rho analytic model for 2-site off-resonance exchange.
This follows the tutorial for adding relaxation dispersion models at:
http://wiki.nmr-relax.com/Tutorial_for_adding_relaxation_dispersion_models_to_relax#The_relax_manual.
The 'TAP03' model was already partly in the manual, however it was listed as unimplemented. All of
the tables and the dispersion chapter text has been updated for the model.
