The indium oxide In2O3 is among the transparent Conducting oxides (TCO) appropriate for solar cells and optoelectronics. The physical properties are based on the electron distribution on the core levels and in the valence band of material.. The knowledge of the electron distribution on the different states is fundamental to predict the possibilities of electron transitions. In this respect, we adopt calculations based on the generalized gradient approximation (GGA) and modified Becke Johnson (mBJ) to show the electron state density. We associate to the numerical simulation the experimental analysis techniques auger electron spectroscopy (AES), electron energy loss spectroscopy (EELS), and UV photoelectron spectroscopy (UPS) of great sensitivity to characterize the material surfaces. The analysis technique AES is used for proving the chemical composition of the In2O3 compound through the In-M45N45N45 and O-KLL signals. The energy loss peak at 16.3 eV on the EELS spectra is related to plasmons. The energy losses lower than 16.3 eV are related to interband transitions (ITs). They arise from the hybridation of states (s, p, and d) of indium and (s, p)of oxygen. The energy loss at 19 eV is mainly related to IT transition from the d states of indium in hybridation with a slight contribution of p and s states of indium and oxygen. The calculation is useful to predict the states from which the interband transitions occur. The EELS associated with UPS constitutes powerful techniques to show the energy states of the electron distribution. The irradiation of In2O3 by the UV photons at, 320 nm leads to the photoluminescence emission at low energy around 580 nm, appropriate to laser applications.