Date of Original Version
Analytic calculations in the Bethe formalism and finite-chain calculations show that the dynamic spin-correlation function in (q, ω)-space of the s=1/2 linear Heisenberg antiferromagnet at T> = 0 in a uniform magnetic field is governed by a double continuum of excitations. Appropriate neutron scattering experiments are expected to show double-peak spectra.
Gerhard Müller, Hans Beck and Jill C. Bonner. Zero-temperature dynamics of the s=1/2 linear Heisenberg antiferromagnet in a magnetic field. J. Magnetism and Magn. Materials 15-18 (1980), 367-368.