DETERMINATION OF THE SIGN OF THE QUADRUPOLE COUPLING-CONSTANT (E(2)QQ) OF SN2-GLASSES BY MOSSBAUER-SPECTROSCOPY( IN SILICATE)

High-field Sn-119 Mossbauer spectroscopy was performed on a range of t in-containing ternary and binary silicate glass systems. All the glass es unambiguously exhibited a positive value for e(2)qQ for the Sn2+ va lence state. Determination of the sign of e(2)qQ indicates that the el ectron distribution around each Sn nucleus is similar at all the tin a toms, which is a significant finding for glasses. These results sugges t that the electronic state of the Sn2+ is dictated by its non-bonding electron orbital, which has strong p(z) character, and which provides the dominant contribution to the electric field gradient present at t he Sn-119 nucleus.