  We construct the scaling limit of the easy axis XXZ chain. This limit is a
subtle combination of approaching the isotropic point, and letting the lattice
spacing to zero to obtain a continuous model with a finite mass gap. We give
the energy difference between the two lowest energy states (the two `vacua')
and analyze the structure of the excitation spectrum of the limiting model. We
find, that the excitations form two sets corresponding to the two vacua. In
both sets the dressed particles are described by Bethe Ansatz like equations
(higher level Bethe Ansatz), and the two sets can be distinguished through a
parameter entering into these secular equations. The degenerations in the
spectrum can be interpreted as originating from an SU(2) symmetry of the
dressed particles. The two particle scattering matrices obtained from the
secular equations are consistent with this symmetry, and they differ in an
overall sign in the two sectors.
