H COSY with Varying Mixing Times for the Coupling

H COSY with Varying Mixing Times for the Coupling 

Since phosphorus and protons are both abundant spin-Vi nuclei, it is simple to design an experiment in which we correlate protons and phosphorus rather than protons with themselves. The result of this experiment, a P,H correlation, is shown in Fig. 26. Again we have the 2D spectrum in the form of a central rectangle and two (previously recorded) ID spectra parallel to the axes. One is the proton spectrum, the other the phosphorus spectrum. The latter of course consists of a single line, and in the 2D spectrum we do not need to look for a diagonal as there cannot be one. 

This is not surprising, as the input of an average coupling constant is part of the set-up of the experiment. In fact the time period 1/J (in seconds) is involved in the experiment, and 1/J increases as J decreases. If the individual experiment is too long, the signal intensity will be decreased by relaxation. 

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