  We have performed inelastic neutron scattering on a single crystal sample of
Sr14Cu24O41 to study the spin dynamics of the Cu2O3 spin ladder layers, and
CuO2 chains. Data collected with incident energies of 50 meV, 200 meV, 350 meV
and 500 meV are best fitted with a dispersion with a spin gap of 32.5+/-0.1 meV
and a maximum of 193.52.4 meV, consistent with a coupling along the ladders,
J|| = 130 meV and a rung coupling J^=72 meV. We find that excitations with an
energy transfer of approximately 11.5 meV can be described solely in terms of a
dimer chain with an antiferromagnetic intra-dimer coupling, J1 = 11.2 meV,
between next-nearest-neighbour Cu ions and a ferromagnetic inter-dimer
coupling, J2 = -1.1 meV. The dimers are separated by two Cu ions providing a
periodicity for the dimer chain of five units.
