Dynamic Processes Studied by Two-Dimensional Exchange Spectroscopy

Abstract

Abstract The investigation of dynamic processes such as chemical exchange, cross-relaxation, nuclear Overhauser effects, spin diffusion, and cross-polarization by 2D spectroscopy has a number of advantages over the ID techniques discussed in § 4.6.1.4, particularly when the system comprises an extended network of exchange processes that occur simultaneously. The 2D methods are most useful for studying slow dynamic processes with rates that are too low to affect the lineshapes. Two-dimensional exchange spectroscopy is therefore particularly well suited for studies of cross-relaxation (transient Overhauser effects) and of spin diffusion in solids. In applications to chemical exchange, the information content of 2D exchange spectra is greatest if the temperature is chosen such that the exchange rate is fast compared to longitudinal relaxation and slow compared to the spectral parameters affected by the exchange.