It is doubtful if this formula is valid for particles with an interior structure. The neutron has zero charge but non-zero magnetic moment, so μ μ S q s ℏ ℏ would be impossible (except ∇ ∇ × × ( Ψ Ψ ∗ ∗ S Ψ Ψ ) would also be zero in this case). For composite particles with a non-zero charge – like the proton which has spin quantum number s=1/2 and μ S = 2.7927· μ N or the deuteron (H-2 nucleus) which has s=1 and μ S =0.8574·μ N – it is mathematically possible but doubtful.