# No Rex

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 R20 or R' depending on the data type.

## Equation for No Exchange in CPMG

$R_{2,\textrm{eff}} = R_2^0$

## Equation for No Exchange in R1rho

$\mathrm{R}_{1\rho}= \mathrm{R}_1\cos^2\theta + \mathrm{R}_{1\rho}{´} \sin^2\theta$

If no R1 values has been loaded, but the R1_fit flag has been turned on, the R1 will be fitted as well.

$\bar{\Omega}_{S,i} = 0.0$ then the Rotating frame tilt angle θ is set to: $\theta = \frac{\pi}{2}$

and as such
$cos^2\theta = cos^2\left( \frac{\pi}{2} \right) = 0.0$

Therefore the fitted R1 values have no meaning for "No Rex" model, if there is no offset.

## Reference

These is no reference for the No Rex model.