The Quantum Spectrum of the Conserved Charges in Affine Toda Theories
  The exact eigenvalues of the infinite set of conserved charges on the multi-particle states in affine Toda theories are determined. This is done by constructing a free field realization of the Zamolodchikov-Faddeev algebra in which the conserved charges are realized as derivative operators. The resulting eigenvalues are renormalization group (RG) invariant, have the correct classical limit and pass checks in first order perturbation theory. For $n=1$ one recovers the (RG invariant form of the) quantum masses of Destri and DeVega. 
M.R. Niedermaier