X-rays induced atomic dynamics in a lithium-borate glass

Abstract

The continuous development of synchrotron-based experimental techniques in the X-ray range provides new possibilities to probe the structure and the dynamics of bulk materials down to inter-atomic distances. However, the interaction of intense X-ray beams with matter can also induce changes in the structure and dynamics of materials. A reversible and non-destructive beam induced dynamics has recently been observed in X-ray photon correlation spectroscopy experiments in some oxide glasses at sufficiently low absorbed doses, and is here investigated in a (Li 2 O) 0.5 (B 2 O 3 ) 0.5 glass. The characteristic time of this induced dynamics is inversely proportional to the intensity of the X-ray beam, with a coefficient that depends on the chemical composition and local structure of the probed glass, making it a potentially new tool to investigate fundamental properties of a large class of disordered systems. While the exact mechanisms behind this phenomenon are yet to be elucidated, we report here on the measurement of the exchanged wave-vector (and thus length-scale) dependence of the characteristic time of this induced dynamics, and show that it follows the same power-law observed in vitreous silica. This supports the idea that a unique explanation for this effect in different oxide glasses should be looked for.

X-ray induced dynamics in borate glasses with different network connectivity

“…4(a)]. This result confirms previous studies of the x-ray beam induced dynamics in oxide glasses [9][10][11][12]. The corresponding values averaged over the curves measured with different x-ray dose rates are reported in Fig.…”

“…[10] for a boron oxide glass, in Ref. [12] for a lithium borate glass, and in Ref. [11] for a series of Rb and Cs borate glasses; a compressed exponential decay (β > 1) has instead been observed in Ref.…”

“…Despite the fact that the x-ray-matter interaction is a well established topic overall, the high brilliance provided by synchrotron radiation and x-ray free electron lasers is giving rise to complex and somewhat unexpected effects [7,8]. One example is the focus here: XPCS experiments have shown that an atomic motion is induced at temperatures well below the glass transition when shining an x-ray beam on an oxide glass [9][10][11][12][13]. The induced motion is present already at relatively low doses, when the average structure remains unaffected.…”

Deciphering the intrinsic dynamics from the beam-induced atomic motions in oxide glasses

“…Recent investigations of microscopic dynamics in oxide glasses by XPCS revealed faster than expected relaxation times in a deep glassy state related to the beam-induced effect (Ruta et al, 2017;Dallari et al, 2019;Pintori et al, 2019;Holzweber et al, 2019). In all of the above cases (Ruta et al, 2017;Dallari et al, 2019;Pintori et al, 2019;Holzweber et al, 2019) the X-ray probe interacts with the sample and causes artificial structural relaxations that otherwise should not occur in the sample.…”

“…Recent investigations of microscopic dynamics in oxide glasses by XPCS revealed faster than expected relaxation times in a deep glassy state related to the beam-induced effect (Ruta et al, 2017;Dallari et al, 2019;Pintori et al, 2019;Holzweber et al, 2019). In all of the above cases (Ruta et al, 2017;Dallari et al, 2019;Pintori et al, 2019;Holzweber et al, 2019) the X-ray probe interacts with the sample and causes artificial structural relaxations that otherwise should not occur in the sample. It was clearly identified that the measured relaxation times scale inversely with the intensity of the X-ray beam (Ruta et al, 2017;Pintori et al, 2019;Holzweber et al, 2019) and that the sample dynamics and beam-induced dynamics are independent processes (Pintori et al, 2019).…”