An experimental study was made of the temperature dependence, from 6 to 300K, of the 4.4eV emission excited at 7.6eV via the conversion between 2 different types of O-deficient centers in silica. The photoluminescence undergoes a thermal quenching above 50K, its amplitude decreasing by a factor of 10, not correlated with changes from 2.1 down to 1.4ns of its lifetime. These experimental features were explained with the occurrence of 2 non-radiative processes arising from the 7.6eV excited state: one pumping the 4.4eV emission and the other accounting for alternative relaxation pathways. The competition between these two rates could be expressed in terms of an Arrhenius law fitting the luminescence quenching with an activation barrier of 0.029eV.

Competitive Relaxation Processes of Oxygen Deficient Centers in Silica. S.Agnello, R.Boscaino, M.Cannas, F.M.Gelardi, M.Leone, B.Boizot: Physical Review B, 2003, 67[3], 033202 (4pp)