Saturation pulse
 

Saturation pulse

I keep getting myself lost when thinking about saturation pulses, a pulse in which there is no magnetisation in the z direction. Now I know a 90 degree pulse rotates polarisation to xy however to make sure we have have got all the magnetisation we do a train of 90 degree pulses. The problem comes if you do two 90 degrees pulse right after each other it is similar to a 180 pulse - a few degrees. So we shall assume we rotate about x. do we have to time each pulse so that the xy magnetisation is pointing in x (so the rotation does nothing)and any z magnetisation will get rotated as normal. The problem with this is that the magnetisation will de phase over time so does that mean there is also a 180 echo when the xy magnetisation is in the y to keep the overall phase?

Is there something i'm missing?

Does the classical idea still work or do i have to look at quantumly and think about emission and stimulation probabilities?



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