NMR measurement of the nuclear shielding isotope shift in molecular hydrogen

Measurements have been made of the isotope shift $\sigma \left({\mathrm{D}}_2\right)-\sigma \left(\mathrm{HD}\right)$ over the temperature range 18 to 296 K in the density range 10 to 850 amagats (one amagat is density at STP). At 296 K in the zero-density limit our value for the shift is 0.0469±0.0005 ppm, an improvement by nearly two orders of magnitude over the existing uncertainty. The predicted but previously unobserved temperature dependence has been found. A density dependence has also been observed.