Advanced Concepts in Pulsed Magnetic Resonance
Hahn’s discovery of spin echoes [8.1] demonstrated that one could defeat the effect of magnet inhomogeneity in obscuring the true width of magnetic resonance lines because the echo amplitude M(2τ) decayed exponentially with 2τ/T 2, where τ is the time between pulses. However, if the magnet inhomogeneity is large, and if the diffusion rate of the nuclei sufficiently great, (math) where D is the diffusion constant and ∂H/∂z the gradient in static field. In some instances, then, the τ3 term might obscure the T 2. Or, conversely, if ∂H/∂z is known, the τ3 term gives one a method of measuring D. The derivation of the diffusion term is given in Appendix G.
KeywordsDipolar Coupling Spin Echo Spin Rotation Knight Shift Pulse Cycle
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