The relaxation dispersion model for no chemical exchange. This if for all SQ CPMG-type data, MMQ CPMG-type data, and R1rho-type data. This model is labelled as No Rex in relax.
Parameters
The No Rex model has the parameter $R_2^0$ or $R_{1\rho}'$ depending on the data type.
Reference
These is no reference for the No Rex model.
Links
The implementation of the No Rex model in relax can be seen in the: