A spectral holographic interpretation arises naturally in nuclear magnetic resonance (NMR) photography from either the intrinsic chemical shift anisotropy of the spin system or the field inhomogeneity due to the applied spatial encoding gradients.We can thus think of NMR photography as arising from a "diffraction" off a spatial-spectral holographic grating.The spatial holographic component arises from a high dielectric constant (>50) of the NMR medium at high field strength (>4 T) when the excitation wavelength is commensurate with the size of the NMR sample; otherwise,it is a volume spectral holographic grating.In this paper,the NMR localized spectroscopy (imaging) equation is derived from the principles of spatial-spectral holography.Holographic properties of storage and programmable time delay and time reversal are shown to follow naturally from this viewpoint and are experimentally demonstrated in an inhomogeneously broadened NMR sample.These ideas are shown to be extendable to complex signal processing functions such as recognition,correlations,and triple products.
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