Elementary Electronic Excitations in Pure Sodium Silicate Glasses

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Abstract
Electronic structure in high‐purity sodium silicate glasses is studied. The spectral dependence of the relative quantum yield of the external and internal photoemission, the luminescence excitation spectra, the luminescence decay, and the polarization degree of the luminescence are measured. The luminescence band at 3.4 eV is created by the intrinsic anisotropic luminescence centre labelled L, whose absorption causes the fundamental absorption tail of high‐purity silicate glasses, where the localized elementary excitations are created by photons. The phonon‐assistent or tunneling delocalization processes produce colour centres. An electron release from the L‐centre leads to the creation of the H‐centre. An electron capture of the L‐centre results in the E‐centre. A model of the structure Na+ ‐ O−‐ Si = is proposed for the L‐centre. Hence the structure for the E‐centre model will be Na0. O−  Si =, but for the H‐centre it will be Na+ O  Si =. The pair of E and H‐centres can probably recombine in a tunneling process.