Distinct orbital contributions to electronic and magnetic structures in La_{4}Ni_{3}O_{10}

High-T_{c} superconductivity has recently been discovered in Ruddlesden-Popper (RP)-phase nickelates under pressure, where the low-energy electronic structure is dominated by Ni d_{x^{2}−y^{2}} and d_{z^{2}} orbitals. However, the respective roles of these orbitals in superconductivity remain unclear. Here, by combining x-ray absorption, electron energy loss spectroscopy, and density functional theory calculations on La_{4}Ni_{3}O_{10} single crystals, we identify ligand holes in the p_{x,y} orbitals of planar oxygen and the p_{z} orbitals of apical oxygen, which hybridize with the Ni d_{x^{2}−y^{2}} and d_{z^{2}} orbitals, respectively. These ligand holes enable orbital-selective O K-edge resonant inelastic x-ray scattering (RIXS) study, which reveals that d_{x^{2}−y^{2}} states dominate the low-energy charge excitations and are more itinerant. We also observe an ∼0.1eV bimagnon through RIXS and Raman spectroscopy. Our results reveal distinct contributions of Ni d_{x^{2}−y^{2}} and d_{z^{2}} orbitals to the electronic and magnetic structure and provide direct experimental insights to understand the RP-phase nickelate superconductors.