Shaped radiofrequency pulses are widely used in nuclear magnetic resonance (NMR) spectroscopy for selective excitation or inversion of magnetization. Efficient, accurate methods for calculating the performance of pulses enable the understanding of existing pulses and help to optimize new pulses. A new approach for approximating the effects of shaped pulses is introduced and applied to some popular shaped pulses as examples. This approach will also be useful in other areas of NMR spectroscopy.

The efficiency of MRI contrast agents can increase by exploiting magnetization transfer effects occurring in slow-rotating nanoparticles containing a paramagnetic metal ion and a large number of exchangeable surface protons, which can increase the water proton relaxation rate. Occurrence of magnetization transfer should also be considered to determine accurate metal–proton distances from the experimental proton relaxation rates for protons farther than 15 Å from the paramagnetic metal.

We studied spin dynamics in nuclear spin systems at low magnetic fields, where strong coupling among nuclear spins of the same kind, here ¹³C, is expected. Such conditions are known to be favorable for coherent polarization transfer. However, to our surprise, interactions with other nuclei, i.e., protons, lead to a breakdown of the strong coupling conditions. By using a two-field nuclear magnetic resonance approach, we can manipulate low field-spin dynamics and reintroduce strong coupling.