Nuclear Magnetism and NMR Spectroscopy

When you say magnet you probably think of a solid metallic body that sticks to a steel object, a refrigerator door for example. AH magnets we know have two poles, north and south. Physicists call such objects magnetic dipoles. When you have one magnet it usually does not matter where its north pole or south pole is pointing. 

It is quite different when you have two magnets they can take two types of positions in space, four positions in total. They attract each other when south is oriented toward north. Fig. 12.7, or they repel or repulse each other when the same poles, for example, north and north, are oriented toward each other. Fig. 12.8. 

Fig 12.7 Two magnets in attractive position a lower energy state 

Fig 12.8 Two magnets in repulsive position a higher energy state 

Ground State + AE Excited state — AE — Ground state 

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