INEPT and the Transfer of Magnetization from H to

This is just following the rules for each individual operator in the product (Fig. 7.15). The resulting product operator, 2SXIZ, can be described as 13C magnetization on the xf axis, antiphase with respect to the z magnetization (a or p state) of its attached H nucleus. Acquisition at this time would yield an FID at the 13C frequency, and Fourier transformation with phase reference - -x would give a carbon doublet with a downfield component of normal phase and an upheld component of opposite phase (upside-down). This is what you will see in your INEPT spectrum an antiphase 13 C doublet. Later, we will see that this spectrum is actually four times as intense as the normal 13C spectrum this is the enhancement part of INEPT. 

There are two important consequences of this method. Both result from the fact that the magnetization that is being observed (13C antiphase doublet) arises from H magnetization that is rotated from its equilibrium state along the z axis by the first 90° proton pulse. The first consequence arises because the lH population difference at equilibrium (sometimes called polarization ) is four times the carbon population difference at equilibrium. This results from the larger energy separation between the a and states for protons  

8 SELECTIVE POPULATION TRANSFER (SPT) AS A WAY OF UNDERSTANDING INEPT COHERENCE TRANSFER 

Now we need to write in the population of each level at equilibrium (Fig. 7.20). According to the Boltzmann distribution, the population of each level will be N/4 times the exponential factor  

The deviation in population from an equal distribution between all four states (N/4) is thus proportional to the energy. For the a ac state, we draw five filled circles (E = —5) to indicate a population of N/4 + 5S where S is (N/4)(AEc/%kT). For the auPc state we draw three filled circles (E = —3), for the Pnoic state we draw three open circles (E = +3), and for the PnPc state we draw five open circles (E = +5) representing a population deficit of 58 (Fig. 7.20). Now look at the population differences at equilibrium for the transitions, 

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