Dynamical Structure Factors for the Heisenberg Chain with Alternating   Exchange
  We discuss the transition strength between the disordered ground state and the basic low-lying triplet excitation for the Heisenberg chain with alternating exchange based on series expansions in the interdimer interaction up to tenth order. We demonstrate that the wave vector dependence of the simple dimer approximation is strongly modified in higher orders. 
M. Mueller and H.-J. Mikeska