</source>
Then $\Omega_S$ is calculated with: $\Omega_{S,i} = \bar{\omega} - \omega_{rf}$, 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$\bar{\omega}$.
<source lang="python">
Delta_omega = shifts[ei][si][mi] - offsets[ei][si][mi][oi]