Proton spin states, inversion polarization transfer

The pulse sequence has a basic polarization transfer portion (Figure 3) which produces a net inversion of one of the proton spin states. Following an X nucleus 90° pulse there exists enhanced magnetization in the X multiplet. The signal enhancement is proportional to the ratio of the mag-netogyric ratios of the two nuclei involved, a factor of 4 for and 10 for l N for X-1h experi-... 

This special pulse sequence uses strong nonselective pulses and gives general enhancement rather than specific sensitivity enhancement, as in SPT. The pulse sequence has a basic polarization-transfer portion that produces a net inversion of one of the proton spin states. Proton transverse magnetization is created by the initial proton 90° pulse and precesses for a period t. The magnetization is then refocused as a spin echo at a time 2r by the action of a 180° proton pulse. Application of a 180° pulse at the midpoint of the 2r delay ensures that the echo is modulated by the scalar coupling, 7ch- If t is chosen to be equal to 1/(4Jch) then at time 2r, the... 

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