[en] We present the non-destructive analysis of aperiodic Mo/Si multilayers by X-ray emission spectroscopy induced by electrons. The Si 3p occupied valence states of the silicon atoms present within these structures are analysed. Because of the great sensitivity of these states to the physico-chemical environment of the Si atoms, it is possible to distinguish the emission from the center of the Si layer (amorphous silicon) to that of the interfacial zones between the Mo and Si layers. Thus, the presence of molybdenum silicides is evidenced in the interfacial zones. It is also shown that the relative proportion of interfacial silicides depends on the deposition conditions