A. Free-induction decay

           
B. Spin Exchange
 

 

- Cross Polarization transfer
- Flip H magnetization to magic angle
- Allow ¹H/¹⁵N to spin-exchange
- Acquire ¹⁵N under ¹H decoupling

- Find the Hartmann-Hahn match at on-resonance condition
- Find the 1H resonance frequency
- Measure the 1H nutation frequency
- Find the Hartmann-Hahn match at off-resonance condition
- Find the phase of the 35.7o pulse

Find the Hartmann-Hahn condition at on-resonance condition

- Use a N-acetyl-Leucine single-crystal sample
- Adjust X channel power level to match the 1H channel power

Find the ¹H resonance frequency

•- - Turn the decoupler power way down

•Sweep the 1H irradiation frequency

         

Measure the ¹H nutation frequency

•-Initial pulse rise time prevent accurate nutation frequency measurement

•Use pre Spin-lock pulse to accurate measure ¹H nutation frequency

Find the Hartmann-Hahn condition at off-resonance condition

•Require phase-continuous frequency switching

•Match the X channel to 1H channel during the offset irradiation (+Df)

•Match the X channel to 1H channel during the offset irradiation (-Df)

•Precede with spin-lock pulse

•No compensation pulse

 

Find the phase of the 35.7o pulse

Typical PISEMA spectra

•The line width (FWHH) is <200 Hz typical for single-crystal

 

Hardware requirement

A. Proton transmitter
    1. DDS (direct digital synthesizer)
    2. Or use small angle phase shifter (PMLG: phase-modulated Lee-Goldburg)
B. Proton / X channel amplifier
    1. Frequent phase inversion may overwhelm protection circuit
C. Probe tuning
    1. use directional coupler to monitor the reflective power
    2. Triple frequency tuning
    3. Steady-state tuning

A.

B.