basic-princ-2

basic-princ-2 - NMR Spectroscopy 2 Signal Detection and...

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NMR Spectroscopy: 2
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Signal Detection and Sensitivity d M /dt d B ± /dt A bulk magnetic moment ( M ) precessing about a static magnetic f eld ( B 0 ) results in a local magnetic f eld ( B ± ) varying in time (d M /dt ² d B ± /dt) The voltage (emf, ± ) induced in the detector coil is proportional to the rate of change of the magnetic F ux in the coil, which in turn is proportional to the rate of change of the oscillating transverse magnetization (Faraday’s Law of Induction) oscillating magnetic f eld generates and emf in the receiver coil
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A bulk magnetic moment ( M ) precessing about a static magnetic f eld ( B 0 ) results in a local magnetic f eld ( B ± ) varying in time (d M /dt ² d B ± /dt) The voltage (emf) induced in the detector coil is proportional to the rate of change of the magnetic F ux in the coil, which in turn is proportional to the rate of change of the oscillating transverse magnetization Thus, sensitivity is dependent on ³ 3 and B 0 2 ! ±² d ³ B /d t ² d M /d t ²´ B 0 M 0 = N ´ 3 B 0 2 h 2 I ( I + 1) /(3 k B T ) S/N ² ( ³ C / ³ H ) 3 = 64 -1 Consider equal numbers of two nuclei with the same value of I (i.e. 1
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This note was uploaded on 11/13/2011 for the course CHEM 4190 taught by Professor Staff during the Fall '08 term at UGA.

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basic-princ-2 - NMR Spectroscopy 2 Signal Detection and...

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