Multiparticle states in the S=1 chain system CsNiCl3 - art. no. 017201

A continuum of magnetic states has been observed by neutron scattering from the spin-1 chain compound CsNiCl3 in its disordered gapped one-dimensional phase. Results using both triple-axis and time-of-flight spectrometers sho w that around the antiferromagnetic point Q(c) = pi, the continuum lies hig her in energy than the Haldane gapped excitations. At 6 K the integrated in tensity of the continuum is about 12(2)% of the total spectral weight. This result is considerably larger than the 1%-3% weight predicted by the nonli near sigma model for the three-particle continuum.