Acoustic and Dielectric Properties of Glasses at Low Temperatures

Acoustic behaviour of normal and densified vitreous GeO2

“…In particular, the origin and the nature of low-energy excitations, which are responsible of anomalies in the acoustic properties of [5,6], is a central question in the physics of disordered solids. These excitations are usually accounted for by local motions of localized structural defects.…”

Low-temperature phonon damping in vitreous silica explored by UV Brillouin spectroscopy

“…The variation of the sound velocity v L as a function of temperature is reported in figure 2, and appears in good agreement, within experimental error, with previous visible and ultrasonic data. Small differences between the ultrasonic data (literature data from [9]) may be associated to the different thermal history of the silica samples.…”

“…This supports the description of the Akhiezer mechanism in terms of equation (3) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 [12] and US, circles [9]. [15], HiResUv, full circles (present work) and full squares [16], BLS, crosses [26] and dots [20].…”

“…The position of the maximum increases smoothly and its amplitude increases almost linearly with increasing frequency. Such behaviour is generally understood in terms of a thermally activated relaxation process with the relaxation time following an Arrhenius type activation law [9].…”

Rotational tunneling in a disordered system: nonequilibrium methane CH4II

“…It is a question whether an orientational "glassy state" can be described by a general distribution function as in the tunneling standard model (STM) of normal glasses (21). There must be some fundamental differences, however.…”