The possibility of formation of a chemical bond between noble gas atoms (Ne, Ar), ion-implanted into silicon, and matrix atoms is treated theoretically in a cluster representation using both, the scattered-wave X a ( S W -X a ) and complete-neglect of differential overlap (CND0/2) electronic structure methods. It is shown that the presence of noble gas atoms in the siIicon lattice results in formation of inner valence molecular orbitals (MO) when Ar and Ne atoms interact with Si atoms. A theoretical analysis is made of the results of possible investigations of these structures by photoelectron spectroscopy measurements.