Measurement of the spectral line shapes for orbital excitations in the   Mott insulator CoO using high-resolution resonant inelastic x-ray scattering
  We establish the spectral line shape of orbital excitations created by resonant inelastic X-ray scattering for the model Mott insulator CoO. Improved experimental energy resolution reveals that the line shapes are strikingly different from expectations in a first principles-based atomic multiplet model. Extended theoretical simulations are performed to identify the underlying physical origins, which include a pronounced thermal tail reminiscent of anti-Stokes scattering on the energy gain side of excitations, and an essential contribution from interatomic many-body dynamics on the energy loss side of excitations. 
L. Andrew Wray, J. Li, Z. Q. Qiu, Jinsheng Wen, Zhijun Xu, Genda Gu,   Shih-Wen Huang, Elke Arenholz, Wanli Yang, Zahid Huss...
cond-mat.str-el