Temperature-Dependent 1s2p Resonant Inelastic X-ray Scattering of CoO

The temperature-dependent 1s2p resonant inelastic X-ray scattering (RIXS) spectra of CoO have been measured with 0.3 eV overall resolution, and the RIXS planes have been analyzed with multiplet calculations. The analysis of the high-resolution 1s2p RIXS plane allows a more detailed determination of the ground-state electronic structure, as compared to Is X-ray absorption spectroscopy (XAS). The apparent absence of interference effects suggests that the lifetime broadening of the pre-edge states is (significantly) reduced from the edge lifetime broadening. The temperature-dependent RIXS planes are explained as a combination of the ground state and first excited state due to thermal population of the excited state, which are a result of the symmetry distortion, 3d spin orbit coupling, and magnetic exchange interactions. No features due to charge transfer and nonlocal transitions are observed due to the relatively small cobalt oxygen overlap as compared to higher valent systems. The successful determination of the spin state and crystal field parameters using hard X-ray experiments promises to make 1s2p RIXS a useful technique for in situ transition metal oxide studies.