Deuteron, magnetic moment

The pioneering experiments on H2, HD and D2 were performed by Kellogg, Rabi, Ramsey and Zacharias in 1939 [3], Their principal objectives were to determine the magnetic moments of the proton and deuteron, and the electric quadrupole moment of the deuteron. The sorry events of 1939 to 1945 brought the work to an untimely... 

The results of the second experiment were announced at a January 1936 meeting of the American Physical Society in St. Louis the magnetic moment of the proton equaled + 2.85 0.15 nuclear magnetons, and the magnetic moment of the deuteron equaled + 0.85 0.03 nuclear magnetons. From these data, the neutron s magnetic moment was deduced to be —2.0 nuclear magnetons. 

The second round of experiments on the hydrogens not only gave the signs of the magnetic moments, they also gave the size of the moments with greater precision. The uncertainty in the proton s magnetic moment was reduced from 10 percent to 5 percent and for the deuteron, the uncertainty was reduced from 26 percent to 4 percent, which were considerable improvements. 

The objective of the 1938 experiments was to measure the magnetic moments of the hydrogen and deuterium nuclei as accurately as possible. In 1938, however, a new sense of promise inspired the members of Rabi s group as they prepared to apply the new resonance method to the hydrogens and to measure the magnetic moments of the proton and the deuteron to a new level of precision. Eventually, this objective was accompHshed successfully, but not without surprises that led to new basic knowledge about the atomic nucleus. 

Seandium is a congener of aluminium and is trivalent in all its chemistry. The only stable isotope, has a sizeable magnetic moment and is therefore a very sensitive NMR nucleus. Lutz (178) determined the magnetic moment with high accuracy and referred it to that of the deuteron. In the same paper an isotope shift of —6-2 ppm is reported for the " Sc resonance of aqueous SCCI3 in light and heavy water. 

Because a deuteron has a much smaller magnetic moment than a proton, it absorbs at a much higher field and so gives no signal in the proton nmr spectrum. Furthermore, its coupling with a proton is weak and it ordinarily broadens, but does not split, a proton s signal even this effect can be eliminated by double irradiation. 

A very small correction was estimated by Salpeter on account of the internal structure of the nucleon the possession of a magnetic moment implies a small change in the electrical potential. This correction is significant for hydrogen, but not for deuterium, since the non-Dirac parts of the magnetic moments of the proton and the neutron in the deuteron are approximately equal and opposite. The Dirac part of the proton moment contributes a negligible amount. 

Morsink and Wiersma recently showed that on deuteration the beat disappeared. This may be understood simply on basis of a threefold reduction of the magnetic moment of the deuteron compared to the proton. Also interesting and consistent with this interpretation was the observation that in a magnetic field the beat disappears. This is due to the fact that in a magnetic field all hyperfine levels are pure-spin states characterized by the quantum numbers Ws, Mj> and therefore in the electronic transition, optical branching no longer occurs. 

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