The spinning nucleus

When exposed to a static magnetic field. Bo, along the z direction, the net result of the torque exerted by B(, on the spinning nucleus is a precession movement of p and p about Bo, known as Larmor precession, whose frequency,... 

In an exterior magnetic field, the torque on the magnetic moment of the spinning nucleus, /aligning force of the intramolecular potential. The corresponding potential energy (nuclear Zeeman effect) is given by ... 

Magnetic environment of the spinning nucleus from which structure is inferred... 

If the rotation rate of Bi is varied through the Larmor frequency of the nucleus, a resonance condition is achieved (NMR), and a transfer of energy from Bi to the spinning nucleus occurs producing an oscillation of the angle between p and Bq. At Bq = IT (1 T = 1 Tesla = 10 kilo-gauss) the resonant frequencies (vq) of the nuclei commonly observed in polymers are listed in Table 20.1. 

The spinning nucleus undergoes precessional motion in the presence of a magnetic field 77q. The frequency of this motion is known as the Larmor frequency and is given by ... 

When placed in a static magnetic field of strength Hq, the magnetic moment, fx, of the spinning nucleus precesses about the magnetic field at a... 

The processional motion of the spinning nucleus is originated by the magnetic interaction of the magnetic elemental moment and the external field. Precession has a characteristic frequency called Larmor frequency Larmor frequency is controlled by the gyromagnetic ratio y as substantial property and the external magnetic field strength Bq... 

The principal source of structural information in high-resolution NMR spectroscopy is the chemical shift, which originates from the shielding of the spin nucleus from the external magnetic field by the small magnetic field induced by the motions of the electrons surrounding the nucleus. Thus, the nucleus experiences an effective field, B = (1 - c)Bq, where n, the shielding constant, is a dimensionless number, usually listed in parts per million. This leads to a small modification of the resonance condition in Equation 6.1 ... 

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