A MEASUREMENT OF THE NUCLEAR MAGNETIC-MOMENT OF THE HE-3 ATOM IN TERMS OF THAT OF THE PROTON

We have measured the ratio of the NMR spin precession frequencies of o ptically pumped low pressure helium-3 and of protons in water, using f ree induction decay. This was done by direct substitution in a flux de nsity of 0,1 T of samples in an accurately spherical 25 mm diameter sa mple cell, without-removing the sample cell from the magnet. The water measurements were corrected to 25-degrees-C. The two sets of measurem ents were each referred to a 10 mm diameter spherical reference water sample which was ratioed out. A new method was devised to measure and correct for the different averaging of the residual inhomogeneities in the magnetic field by the helions and by the protons in the water. Ou r final result is mu(h) (He-3)/mu(p)' = -0,761 786 131 3(33). Using th e CODATA 1986 recommended value for gamma(p)' gives gamma(h)/2pi = 32, 434 092 1(97) MHz T-1. Combining the result with a measurement of gamm a(h)(He-3)/gamma(p)(H-2) gives the shielding factor of H-2 as sigma(H- 2) = 26,350(19) x 10(-6), in good agreement with a theoretical value. Combining our result with a measurement of mu(p)'/mu(B) yields mu(h)(H e-3)/mu(B) = -1,158 671 471(14) x 10(-3).