  We report on the most complete investigation to date of the 4f-electron
properties at the gamma-alpha transition in elemental Ce by resonant inelastic
x-ray scattering (RIXS). The Ce 2p3d-RIXS spectra were measured directly in the
bulk material as a function of pressure through the transition. The spectra
were simulated within the Anderson impurity model. The occupation number nf was
derived from the calculations in both gamma- and alpha-phases in the ground
state along with the f doubleoccupancy. We find that the electronic structure
changes result mainly from band formation of 4f electrons which concurs with
reduced electron correlation and increased Kondo screening at high pressure.
