Remarks on excited states of affine Toda solitons
  The identification in affine Toda field theory of the quantum particle with the lowest breather allows us to re-interpret discrete modes of excitation of solitons as breathers bound to solitons, and thus to investigate them through the proposed soliton-breather S-matrices. There are implications for the physical spectrum and for the semiclassical soliton mass corrections. 
G.M. Gandenberger and N.J. MacKay