Acceleration of atomic dynamics due to localized energy depositions under X-ray irradiation

Abstract

The effect of the absorption of hard X-ray photons on the solid-state dynamics, at energies below the defect creation threshold, is considered. First, it is shown that due to the sensitivity to parameter choices, the present state of the theoretical description of photon-electron-lattice coupling cannot decide on whether the local energy deposition due to the absorption of single photons leads to an acceleration of atomic dynamics at fluences before macroscopic effects due to sample heating set in. Second, a direct study of the dynamics under different incident photon fluxes by atomic-scale X-ray Photon Correlation Spectroscopy (aXPCS) is reported, which provides an upper bound of 0.005 additional atomic jumps per absorbed photon of 8 keV. The relevance of such considerations for emergent experimental methods, such as studying atomic dynamics using X-rays as probes, is pointed out.