  The transition from dimerized to uniform phases is studied in terms of
spectral weights for spin chains using continuous unitary transformations
(CUTs). The spectral weights in the S=1 channel are computed perturbatively
around the limit of strong dimerization. We find that the spectral weight is
concentrated mainly in the subspaces with a small number of elementary triplets
(triplons), even for vanishing dimerization. So, besides spinons, triplons may
be used as elementary excitations in spin chains. We conclude that there is no
necessity to use fractional excitations in low-dimensional, undoped or doped
quantum antiferromagnets.
