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=== spin lock offset ===
The offset is in the literature noted as $\Omega_S$, where $\Omega_S$ is the (Ex. $^{15}$N) resonance offset from the spin-lock carrier.
Note that $\Omega_S$ is dependent of the [[wikipedia:Chemical_shift | chemical shifts]] $\delta$ in ppm for the nuclei of interest, and is first calculated later.
In the literature, the values are often stated as "offset", "carrier offset", "offset of the spin-lock pulse" with values given in Hz, and can have values from 0-500 to 10-20.000 Hz.<br>
These values reflects offset frequencies to the carrier frequency, and in relax is noted as '''"Spin-lock offset, the frequency of of the rf field"''' : $\mathbf{\omega_{rf}}$.
Relax needs input for $\mathbf{\omega_{rf}}$ in ppm, and converts to the rad/s, with the following function calls.