SPIN-ROTATION EFFECTS IN BOUNDED SPIN-DIFFUSION

In the NMR theory of paramagnetic fluids, the fast-diffusion regime (sometimes refered to as ''bounded diffusion'') refers to the situation where the spins diffuse across the sample enclosure before they substantially dephase die to inhomogeneities in the static magnetic field. We consider this regime with the additional effects of identical-particle spin rotation as described by the Leggett equation for Fermi liquids. We also consider the effects of finite bur small polarization. We find that the spin-rotation effect can incorporated into the fast-diffusion perturbation scheme, even for large values of the spin-rotation parameter, mu M, and arbitrary tipping angles. WE ob obtain approximate solutions for the fr ec induction decay (FID), the FID lineshape, and spin-echo height. For short times the FID exhibits ringing at the linear spin-wave frequency, while for long times the magnetization decays at the pure diffusion rate, but with a shift in the Larmor frequency which depends on the initial tip angle. For spin-echo experiments on a system of isolated pores, we consider rite effect of the pore-size distribution on the spin-echo data.