NMR Midterm Solns

NMR Midterm Solns - o 15 x 1 2 Beginning with Pulse 90 on...

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NMR Midterm Sol’ns. 15. T 1 dictates how long it will take to re-establish thermal equilibrium after a pulse, so it determines the repetition rate (the time between experiments). T 2 indicates the lifetime of the FID, so it determines the acquisition time (sampling time). 16. To selectively excite (or invert) any single resonance, a longer pulse is required because it has a narrower excitation profile (the excitation profile of any pulse is given by its Fourier transform). 17. The solution is the same as the INEPT example from class, except that coherence is being transferred from a heteronucleus to 1 H instead of the other way around.
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Unformatted text preview: o 15 x 1 2 Beginning with Pulse 90 on N: This is followed by a j-coupling evolution period, which only effects the coherence term: cos( ) sin( ) assuming a perfect transfer ( z z z y y z x z x I S I S S J I S J I S ρ π τ = + =-= -+ = o 1 15 3 1 4 1 = ). 2 Then, simultaneous 90 pulses on H and N: This is followed by another j-coupling evolution period to refocus the new H coherence. cos( ) sin( ) assuming perfect refo y z y z x x J I S I S J I J I τ = =-= -1 cusing ( = , because the 2 coupling is between one pair of spins). J...
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This document was uploaded on 01/03/2012.

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