RELAXATION-TIMES OF MOLECULAR-IONS OH- IN GLASSES AT VERY LOW-TEMPERATURE

This paper presents a detailed study of the temperature dependence of the longitudinal relaxation time T1 and of the coherence time T2 of a population of ionic molecular impurities in silica glass. Electric dipolar echoes taken in a temperature range 4-22 mK and a frequency of 370 MHz show that T1 is governed by a one-phonon process; consequently T1 varies like T-1; experimental data show that T2 also varies like T-1 and this in contradiction with predictions which lead to T-2. The relaxation of the spontaneous and stimulated echoes shows that there is a wide distribution of relaxation times (T1 and T2) ; from the amplitude of the signal it is also possible to extract both the longitudinal and the transverse electric moment; the coupling constant of the impurities with the strain is found to be as large as 3 eV. © 1979 Plenum Publishing Corporation.