Accelerated multidimensional NMR data acquisition by varying the pulse sequence repetition time

(Chemical Equation Presented) Proposed is a simple method for shortening the data acquisition time in multidimensional NMR experiments based on variation of the repetition time (VRT). The repetition time is modulated (usually shortened) in concert with incrementing one or all of the evolution periods. The shortening of the data acquisition time is a consequence of accelerated pulsing. Initially, the pulsing is slow, and it is progressively accelerated toward the outskirts of the evolution domains. Pulsing modulation affects the longitudinal magnetization available for detection, causing line broadening during data acquisition, in complete analogy to filtering during data processing. In VRT, the only difference is that the filter is a function of longitudinal relaxation time. However, most often the resulting broadening is masked by the limited size of the evolution domain, so the overall effect of VRT is a slight reduction of the signal-to-noise ratio. The method is easy to implement in most multidimensional experiments since it only replaces the constant repetition time by a suitable VRT function. It is shown that in a VRT-NOESY-HSQC 3D experiment in 10 mM ¹³C natural-abundance sucrose, the spectrum quality is virtually unchanged even when the data acquisition time is halved.