Phase 2D spectra

Fig. 5.8 Buttons for phasing 2D spectra available with the Correct the Phase button.

The product operator formalism is normally based on Cartesian coordinates because that simplifies most of the calculations. However, these operators obscure the coherence order p. For example, we found (Eq. 11.80) that products such as IXSX represent both zero and double quantum coherence. The raising and lowering operators I+ and I are more descriptive in that (as we saw in Eq. 2.8) these operators connect states differing by 1 in quantum number, or coherence order. We can associate I+ and I with p = +1 and — 1, respectively, and (as indicated in Eq. 11.79) the coherences that we normally deal with, Ix and Jy, each include both p = 1. Coherences differing in sign contain partially redundant information, but both are needed to obtain properly phased 2D spectra, in much the same way that both real and imaginary parts of a Fourier transform are needed for phasing. 

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