11 - NMR Theory 2 - Practical aspects of NMR data...

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1 Practical aspects of NMR data collection Read chapter 2 and section 5.1 The sample is subjected to irradiation by one or more radio-frequency ( rf ) fields (B 1 , B 2 , etc.). Under the effect of B 1 applied along x, M is rotated into the xy plane perpendicular to Bo.
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2 The transverse magnetization precesses under the influence of Bo at the resonance (or Larmor ) frequency ν o and induces a voltage in the detection coil. As soon as it is perturbed, the system starts to return to equilibrium, and the transverse magnetization decays with time. The free induction decay is recorded as a function of time and its frequency content is analyzed by Fourier transformation . The FID contains both the decay information (exponential envelope) and the Larmor frequency information The NMR signal: Voltage versus time
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3 The NMR spectrum: intensity versus frequency. The natural lineshape is a Lorentzian. After FT, What frequencies are there? Play note by note…
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4 … or drop the piano and analyze the resulting sound In Fourier transform spectroscopy, a short pulse at radiofrequencies (rf) and of sufficient power is applied
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This note was uploaded on 10/08/2009 for the course CHEM 439 taught by Professor Falzone,c during the Spring '08 term at Pennsylvania State University, University Park.

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11 - NMR Theory 2 - Practical aspects of NMR data...

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