The molecular-beam magnetic-resonance method for measuring nuclear moments has been applied to the proton and the deuteron. In this method the nuclear moment is obtained by observing the Larmor frequency of precession ($\nu =\frac{\mu H}{\mathrm{hI}}$) in a uniform magnetic field. For this purpose HD and ${\mathrm{D}}_2$ molecules are most suitable because they are largely in the state of zero rotational momentum. Very sharp resonance minima are observed which makes it possible to show that the observed values of $\frac{\nu }{H}$ are independent of $H$, and to make a very accurate determination of the ratio $\frac{{\mu }_P}{{\mu }_D}$. With molecules of orthohydrogen in the first rotational state a radiofrequency spectrum of six resonance minima was obtained. This spectrum when analyzed yields a set of nine energy levels from which are obtained (1) the proton moment from its Larmor precession frequency; (2) the proton moment from the magnitude of the dipole interaction between the two proton magnetic moments (the directly measured quantity is $\frac{{\mu }_P}{r^3}$); and (3) the value of the spin orbit interaction constant of the proton moment with the rotation of the molecule or the magnetic field $H^{\prime }$ produced by the rotation of the molecule at the position of the nucleus. The numerical results are ${\mu }_P=2.785\mathrm{}\pm 0.02$ nuclear magnetons; ${\mu }_D=0.855\mathrm{}\pm 0.006$ nuclear magneton; $\left(\frac{{\mu }_P}{{\mu }_D}\right)=3.257\mathrm{}\pm 0.001$; $H^{\prime }=27.2\mathrm{}\pm 0.3$ gauss; $\frac{{\mu }_P}{r^3}=34.1\mathrm{}\pm 0.3$ gauss which gives ${\mu }_P=2.785\mathrm{}\pm 0.03$ nuclear magnetons. To within experimental error there is no disagreement of the results of these direct measurements with those from atomic beam measurements of the h.f.s. $\Delta \nu$ of the ground states of H and D.

• Received 31 July 1939

DOI:https://doi.org/10.1103/PhysRev.56.728