Quadrature detection principle

I is necessary if one is seeking to obtain the very high resolution spectra I which can, in principle, be obtained from this particular sample. I. Quadrature detection was used, with sequential acquisition of the two I quadrature signals ( 1.4.2). Eight transients were collected using 7t/4 I pulses and a 5 s relaxation delay. In this sample, the spin-lattice relaxation is very slow and long recycle times (15 s) are necessary to avoid errors in signal intensities ( 1.4.7). 

A somewhat similar to the above, but this time with the quadrature detection with sensitivity enhancement, was used by Ding and Gronenborn to measure different coupling involving back-bone nuclei. In one version of the method the J-evolution was introduced into 2D [ H, N]-HSQC-like spectrum by synchronising it with the chemical shift using the accordion principle. The... 

We consider now an important example of phase cycling that is used in both ID and 2D NMR, namely the suppression of artifacts resulting from imperfections in the hardware used for quadrature phase detection. We detail the principles and procedures involved in this example as a prototype for many more complex phase cycling procedures that we mention more briefly in later chapters. 

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