Radiation damping effects in solvent preirradiation experiments in NMR

Proton magnetization in water under radio-frequency irradiation is monitored by recording the signals excited with low-power long pulses. Radiation damping is quite effective when the irradiation time is not long, but is greatly suppressed by 2 s irradiation. Since radiation damping is homogeneous in the mechanism of line broadening, it can be removed by on-resonance irradiation for a sufficient long time and with proper rf strength. Experiments and computer simulations indicate that the spin-locking effect, which occurs due to the inhomogeneity of the fields, is the main reason for unclean solvent suppression in preirradiation experiments.