Charge excitations were studied for stipe-ordered 214 compounds,
La5/3Sr1/3NiO4 and 1/8-doped La2(Ba, Sr)xCuO4
using resonant inelastic x-ray scattering in hard x-ray regime. We have
observed charge excitations at the energy transfer of 1 eV with the momentum
transfer corresponding to the charge stripe spatial period both for the
diagonal (nikelate) and parallel (cuprates) stripes. These new excitations can
be interpreted as a collective stripe excitation or charge excitonic mode to a
stripe-related in-gap state.Comment: 5 pages, 4 figure