Probing the dynamics of B₂O₃ across the glass transition: an X-ray photon correlation spectroscopy study

X-ray photon correlation spectroscopy is used to study the dynamics of the glass former B2O3 across the glass transition temperature, Tg. The obtained data confirm that while the structural relaxation drives the density rearrangements in the liquid phase, a beam-induced dynamics is the dominant effect around and below Tg. The use of a hybrid photon counting detector allows us to obtain high-quality correlation functions with a characteristic decay time down to a second. The characteristic time of the induced dynamics displays a linear dependence on the inverse of the absorbed X-ray power over the whole observed range, i.e. up to powers of 0.2 eV/atom/s. Up to these values, then, an X-ray irradiated B2O3 glass sample explores structurally equivalent configurations on a timescale dictated by the absorbed power.