NMR SPECTROSCOPY

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 NMR SPECTROSCOPY 

  • NMR depends on the absorption of energy when the nucleus of an atom is excited from its lowest energy nuclear spin state to the next higher one. 
  • The nuclear energy levels are produced by keeping nuclei in a magnetic field.
  • The NMR spectrum is produced by EM radiation in the radio wave frequency region (60-500MHz). 
  • NMR spectroscopy deals with nuclei having I=1/2. The spin quantum number (I) is related to the atomic number and mass number of the nucleus.
  • Elements with either odd mass numbers or add atomic numbers have the property of nuclear spin.
  • Radio waves are the lowest energy form of EM radiation. This energy is too small to vibrate, rotate or excite an atom or molecule.
  • It is sufficient to influence the nuclear spin of the atoms of a molecule. 

Principle of NMR

The nucleus of an atom is positively charged, when it spins it develops a magnetic field and acts like a tiny bar magnet with a magnetic moment (µ)
µ= I(I+1)1/2 h/2 π
 The spin quantum number of the nuclei that can have zero, integral or half-integral values and h is Planck’s constant. 
When an external magnetic field is applied the nuclei align themselves either with or against the field of the external magnet.

Location: United States

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