Spin angular momentum discovery

Physicists pioneered NMR spectroscopy in the 1940s, and used it to understand the bizarre properties of nuclear spin angular momentum. The discovery of chemical shifts and scalar coupling made it universally applicable to chemistry, and every major chemistry department in the country has NMR spectrometers which use this effect. Many... 

The discovery of this interaction led to the postulation that an atomic nucleus possesses a spin-angular momentum represented by the spin angular momentum vector h, where I is the nuclear spin and h is Planck s constant, h, divided by Itt. It has been found experimentally that I is an odd integer multiple of for nuclei of odd atomic mass numbers (isotope number), zero for nuclei of even atomic mass numbers and even nuclear charges (atomic number), and an integer for nuclei of even atomic mass numbers and odd nuclear charges. The nuclei that we are concerned with here, H, C, and F, have an I of 5. 

Quantitative theories for the chemical shift and nuclear spin-spin interaction were developed by Ramsey (113) soon after the experimental discoveries of the effects. Unfortunately the complete treatments of these effects involve rather detailed knowledge of the electronic structures of molecules and require evaluation of matrix elements of the orbital angular momentum between ground and excited electronic states. These matrix elements depend sensitively on the behavior of the wave function near... 

The separated 3D wave equation can no longer describe any of these fundamental rotations. For this reason, the discovery of electron spin necessitated its introduction into quantum theory as another ad hoc postulate. The anomalous consequence is the unphysical situation of a point particle with spin. Only part of the spin function survives solution of the 3D wave equation, in the form of a complex variable interpreted as orbital angular momentum. In the so-called / -state, it has the peculiar property of non-zero orbital angular momentum with zero component in the direction of an applied magnetic field. This is the price to pay for elimination of spherical rotation. 

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