Determination of deuteron quadrupole moment from calculations of the electric field gradient in ${\mathrm{D}}_2$ and HD

We have carried out an accurate determination of the quadrupole moment of the deuteron nucleus. The evaluation of the constant is achieved by combining high accuracy Born-Oppenheimer calculations of the electric field gradient at the nucleus in the ${\mathrm{H}}_2$ molecule with spectroscopic measurements of the quadrupolar splitting in ${\mathrm{D}}_2$ and HD. The derived value is $Q=0.285783(30$) fm${}^2$.