Section4: An assembly of non-interacting spins

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# Section4: An assembly of non-interacting spins - PowerPoint PPT Presentation

Section4: An assembly of non-interacting spins. Real systems consist of many nuclear spins. In a static magnetic field, B =B z k , there is a degeneracy of spin states. Population difference, n , is given by BOLTZMANN STATISTICS:. Boltzmann equation. Many spin system:.

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Presentation Transcript

Section4:

An assembly of non-interacting spins

• Real systems consist of many nuclear spins.
• In a static magnetic field, B =Bzk, there is a degeneracy of spin states.
• Population difference, n, is given by BOLTZMANN STATISTICS:

Boltzmann equation

Many spin system:

All spins have the same precession frequency,wl=gBz

BUT random phases.

So Mx and My = 0, and net magnetisation is in z-direction.

Bz

a

M

b

Magnetic Resonance:

Lecture 5:

4) An ensemble of spins

4.2 Effect of B fields on ensemble of spins

(p 31 & p258 Levitt)

4.3 Bloch equations

4.4 The NMR Signal

4) The NMR Spectrometer