Density, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) measurements of Ge_1−xSn_xSe₂ within 0.00 ⪕ x ⪕ 0.6 have been obtained. Upon increasing the Sn content, the density measurements show a non-monotonic decrease, while the differential scanning calorimetry measurements show a monotonic decrease of the glass transition temperature. The X-ray diffraction measurements on these glasses give interference functions which have first sharp diffraction peaks (FSDP) indicating the presence of intermediate range order (IRO). The X-ray photoelectron spectroscopy measurements were used to determine the plasmon energies from the L₃M_4,5M_4,5 selenium Auger peaks which may be looked upon as being determined by the local electron density about the selenium atoms. It is found that the plasmon energies deduced from the Auger peaks change markedly with the Sn content in these glasses. These results are consistent with the fragmentation of the molecular cluster network model proposed by Mikrut and McNeil.