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Resonance condition

Resonance condition. Pulse. A coil of wire placed around the X axis will provide a magnetic field along the X axis when a direct current is passed through the coil. An alternating current will produce a magnetic field which alternates in direction.

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Resonance condition

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  1. Resonance condition

  2. Pulse • A coil of wire placed around the X axis will provide a magnetic field along the X axis when a direct current is passed through the coil. • An alternating current will produce a magnetic field which alternates in direction. In magnetic resonance, the magnetic field created by the coil passing an alternating current at the Larmor frequency is called the B1 magnetic field. When the alternating current through the coil is turned on and off, it creates a pulsed B1 magnetic field along the X' axis. http://www.cis.rit.edu/htbooks/nmr/inside.htm

  3. The spins respond to this pulse in such a way as to cause the net magnetization vector to rotate about the direction of the applied B1 field. The rotation angle depends on the length of time the field is on, , and its magnitude B1. a = 2 p g t B1. In our examples, will be assumed to be much smaller than T1 and T2. http://www.chem.queensu.ca/FACILITIES/NMR/nmr/webcourse/index.htm

  4. Pulse • Application for a specified period of time of a radio-frequency pertubation which excites the spin system non-selectively over a given bandwidth • t time period; bandwidth=1/t • Flip-angle of a pulse: a = 2p g t B1 B1:strength of r.f. field • For proton 90 pulse is about 10 W and t ~ ms t

  5. Flip Angle of the pulse http://www.chem.queensu.ca/FACILITIES/NMR/nmr/webcourse/index.htm a = 2pgt B1

  6. Perturbation by RF Pulse

  7. Pulse Sequence

  8. Fourier Transform Data Analysis Time domain (t) The Pulse FT NMR Experiment 90º pulse Experiment (t) equilibration detection of signals

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