Nuclear Spin-Spin Interaction Energy in the Hydrogen Molecule

An accurate theoretical estimate of the interaction energy of the two proton magnetic moments in the $v=0\mathrm{}$, $J=1\mathrm{}$ vibrational-rotational level of the electronic ground state of ${\mathrm{H}}_2$ is obtained. Agreement with the experimental value for the nuclear spin-spin interaction energy is found to be within 1 part in ${10}^3$. This is of the order of magnitude of the experimental error.