Quadrupole moment of the deuteron from a precise calculation of the electric field gradient inD2

Abstract

The electric field gradient along the molecular axis at the nucleus in ${\mathrm{D}}_2$ has been calculated at $R=1.4\mathrm{}$ a.u. by means of the Kołos-Wolniewicz 54-term Born-Oppenheimer wave function. The result is a confirmation of the Reid-Vaida value. A nonadiabatic calculation using a 540-term wave function (explicitly containing the vibronic component) also confirms the earlier value of the electric field gradient and necessarily, therefore, the predicted quadrupole moment of the deuteron (i.e., $Q=0.2860\mathrm{}\pm 0.0015$ ${\mathrm{fm}}^2$).