Nuclear Radiofrequency Spectra ofH2andD2in High and Low Magnetic Fields

A new molecular beam apparatus of improved design is described which utilizes, among other improvements, a long homogeneous magnetic field with two separated oscillatory fields for high resolution and a method of phase shifting of the two fields which permits more accurate data-taking. The apparatus has been used to study the nuclear radiofrequency spectrum of ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ in magnetic fields of 1600 gauss and 6 gauss. The results are found to be consistent with Ramsey's theoretical expressions, provided the adjustable parameters are suitably selected. For ${\mathrm{H}}_2$ the values for these parameters are that $c$ equals 113,800±210 cps and $d$ equals 57,680±40 cps, while for ${\mathrm{D}}_2$ $c$ equals 8790±60 cps and $d$ equals 25,240±20 cps. These values for the parameters imply that the rotational magnetic field $H^{\prime }$ at the nucleus in ${\mathrm{H}}_2$ is 26.73±0.05 gauss while in ${\mathrm{D}}_2$ it is 13.44±0.09 gauss, that the internuclear spacing $r$ in ${\mathrm{H}}_2$ is such that when averaged over the zeroth vibrational state and the first rotational state ${〈\frac{1}{r^3}〉}^{-\frac{1}{3}}$ equals (0.74673±0.00018)×${10}^{-8\mathrm{}}$ cm, that the deuteron quadrupole interaction $eQ\left(\frac{{\partial }^2{V}^e}{\partial {z_0}^2}\right)$ equals (1.4907±0.0015)×${10}^{-21\mathrm{}}$ erg, that the quadrupole moment $Q$ of the deuteron equals (2.738±0.014)×${10}^{-27\mathrm{}}$ ${\mathrm{cm}}^2$, and that the nuclear magnetic shielding constant $\sigma$ for ${\mathrm{H}}_2$ is (2.65±0.03)×${10}^{-5\mathrm{}}$.