Changes

Then $\Omega_S$ is calculated with: $\Omega_{S,i} = \bar{\omega}_{S,i} - \omega_{rf}$, where $\bar{\omega}$ is the population averaged Larmor frequency of the spin and comes from the conversion of the [[wikipedia:Chemical_shift | Chemical Shifts]] $\delta_{S,i}$ to frequency $\bar{\omega}_{S,i}$.