  We report resonant inelastic x-ray scattering experiments of the orbital
ordered manganite LaMnO3. When the incident photon energy is tuned near the Mn
K absorption edge, the spectra reveal three features at 2.5 eV, 8 eV and 11 eV.
The 8 eV and 11 eV peaks are considered charge-transfer type excitations. On
the other hand, theoretical calculations identify the 2.5 eV peak as an orbital
excitation across the Mott gap, i.e. an electron excitation from the lower
Hubbard band with the d3x2-r2 and d3y2-r2 orbital characters to the upper
Hubbard band with the dy2-z2 and dz2-x2 ones. The observed weak dispersion and
characteristic azimuthal angle dependence of this new type of excitations are
well reproduced by the theory which includes orbital degeneracy and strong
electron correlation.
