How NMRW orks

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					        Spectra

Nuclear Magnetic Resonance
         NMR
           Matter and Light
• Matter and light can interact
• Energy in light can be passed directly on to
  matter
• Energy in matter can be released as light

                  • E = hf

                                     -34
• h is Plancks constant 6.626 x 10         Js
LIGHT
               Matter and Light
• Interaction can only
  take three forms

• Absorption

• Emission

• Relaxation
                 Absorption
• Elements in the sun absorb some light
• A spectra of sunlight shows gaps




• Newton thought this was due to the prism
LIGHT
               Absorption

        • Excited State




        • Ground State
                  Emission
• Excited atoms emit light when they react
• An emission spectrum is just lines.




• The wavelength can be used to calculate the
  energy emitted
LIGHT
           Matter and Light

        • Excited State




        • Ground State
                  Relaxation
• Relaxation can be
  slow process

• The electron may not
  fall straight back

• It may go back in
  small vibration and
  rotation energy levels.
                 Using Light
• Ultra Violet   • Organic molecules with rings
                   and ring systems
• Visible        • Atomic absorption and emission
                   spectroscopy
• Infra red      • Identification of functional
                   groups by vibration
• Microwave      • Rotations of molecules

• Radio waves    • Interaction with nuclear
                   alignment in a magnetic field
Using Light
                    NMR
• In strong magnetic
  fields
• Nuclei in certain
  atoms
• Align with or against
  the field
• Ground state is with
  the field.
                    NMR
• Radio waves will
  excite the nuclei
• They flip from normal
  to excited

• The frequency of the
  radio wave required
  can be used in
  identification
Radio
waves
            Matter and Light
• So the energy level
  diagram for• NMR is State
                 Excited
  the same as for other
  light interactions.



            • Ground State

				
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posted:9/15/2012
language:English
pages:13