Test== Setting up relax_disp.spin_lock_offset and relax_disp.spin_lock_field == [http://www.nmr-relax.com/manual/relax_disp_spin_lock_offset.html | Manual on relax_disp.spin_lock_offset ] relax_disp.spin_lock_offset(spectrum_id=None, offset=None) [http://www.nmr-relax.com/manual/relax_disp_spin_lock_field.html | Manual on relax_disp.spin_lock_field ] relax_disp.spin_lock_field(spectrum_id=None, field=None) [http://www.nmr-relax.com/manual/Dispersion_model_summary.html | Refer to the manual for parameter explanation] Comparing to Figure 1 and 10 the reference. Palmer, A.G. & Massi, F. (2006). Characterization of the dynamics of biomacromolecules using rotating-frame spin relaxation NMR spectroscopy. Chem. Rev. 106, 1700-1719 [http://dx.doi.org/10.1021/cr04042875 | DOI: ] The offset is in the literature noted as Omega, where Omega In the literature, the values are often stated as "offset", "carrier offset", "offset of the spin-lock pulse" with values given in Hz, and have values from 0-500 to 10-20.000 Hz. The relax function relax_disp.spin_lock_offset() requires these values to be provided in ppm. And here comes the trouble. Does the Hz frequency refers to RF fields applied at the 1H Larmor frequency or 15N frequency? At page 1708 is states that w_1S = w_1 and w_eS = w_e.And in pulse sequence it states that: deltadof2 = getval("deltadof2"), /* offset for N15 spinlock */