Deuteron D-state admixture ($P_D={\int }_0^{\infty }|u_D(r){|}^{2}dr$)

The deuteron has a dominant ${}^3{S}_1$ component and a smaller ${}^3{D}_1$ component coupled by the nuclear tensor force. The electric quadrupole moment rules out a purely isotropic S wave spatial state. A D-state probability depends on the chosen nuclear Hamiltonian and current approximation; it is not an independently model-free observable.