Nuclear Radiofrequency Spectra ofD2andH2in Intermediate and Strong Magnetic Fields

The molecular beam apparatus previously described has been improved and has been used to make measurements on the nuclear radiofrequency spectrum of ${\mathrm{H}}_2$ at intermediate and high magnetic fields. These measurements are the first to provide a test of the theory of molecular ${\mathrm{H}}_2$ at intermediate magnetic fields and provide a more accurate test of the theory at strong magnetic fields. Agreement of the intermediate field results with the predictions from the high and very low field measurements was found to within experimental error. The numerical values of the interaction constants $c$ and $d$ occurring in the Hamiltonian and the physical quantities that can be calculated therefrom were improved by these measurements. The best values of $c$ and $d$ for ${\mathrm{H}}_2$, obtained from the intermediate field measurements, are 113 904±30 cps and 57 671±24 cps, respectively. Measurements were also made on the nuclear spectrum of ${\mathrm{D}}_2$ at a stronger external magnetic field than any used previously. These measurements improved the numerical values of interaction constants for ${\mathrm{D}}_2$. The best values of $c$ and $d$ for ${\mathrm{D}}_2$ are 8788±40 cps and 25 237±10 cps, respectively. The comparison of $c$ for ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ indicates that the magnetic shielding of the nuclei should differ in these molecules in accordance with $\frac{{}_{}{}^{\mathrm{D}}{}_{}{}^{}\sigma }{{}_{}{}^{\mathrm{H}}{}_{}{}^{}\sigma }=1.006\mathrm{}\pm 0.005$.