Here, M mol is the magnetic moment vector for the nucleus of interest, which, like the external field B mol 0 , is a parameter in the Hamiltonian H(R). Any observable expressed in the molecule-fixed frame will be independent from the Euler angle ϕ. This is in particular true for the electronic Helmholtz free energy F (R) = F (χ, θ), which is identical in the laboratory frame and the molecule-fixed frame since it is a scalar. Transforming the average induced field vector back to the laboratory frame gives the ⟨B ind ⟩ el (R) occuring in Eq. (11),