N(=1,2,3) DIMENSIONAL, FT-EPR SPECTROSCOPY AND MNDO CALCULATIONS FOR THE INTERPRETATION OF THE HC1 CENTER DETECTED IN SILICATE GLASSES

Silicate glass was exposed to gamma-ray irradiation and studied using n(=1,2,3) dimensional and Fourier Transform Electron Paramagnetic Reso nance (FT-EPR) spectroscopy. A single spectrum was detected assigned t o the HC1 centre. The MNDO calculations and the analysis of the spectr a revealed that the hole is trapped on non-bridging oxygen atom. Addit ionally, the FT-EPR signal of the HC1 centre was detected and analysed by a formalism introduced for the first time in glasses. The simulati on was best accomplished assuming that the echo decay is modulated by the nuclear spin of a single alkali metal ion in the close proximity o f the centre. The simulation was not exquisite due to the oversight of the contribution of other long distant cations to the ESEEM spectrum interacting with the unpaired state. It appears from the first rough e stimation that the cation in close proximity of the HC1 centre interac ts with a fairly large number of surrounding cations.