Spin dynamics at very high spin polarization

The dynamics for dipole-coupled nuclear spin systems under conditions of high spin polarization are investigated both theoretically and numerically. Quantum spin simulations were performed which demonstrate that the transverse magnetization decays more rapidly as θ→π∕2, where θ is the initial tip angle applied to the spins. Simple analytical models are used to demonstrate the increased decay of the transverse magnetization as θ→π∕2. Calculations of the free induction decay (FID) up to the fourth moment are consistent with the increased decay of the FID with increasing tip angle. The increased decay of the FID is a result of increased spectral interference amongst the various spectral transitions.