Q-dependence of the fast secondary relaxation in metallic glass-formers during the liquid-to-glass transition

During a recent XPCS beamtime at DESY we probed the dynamical response of a metallic glass (MG) of Zr46.8Ti8.2Cu7.5Ni10Be27.5 (vit4) and we obtained the first experimental evidence of a fast secondary beta-relaxation process in a glass, prior to the main structural relaxation which results in a double decay of the intermediate scattering functions (ISFs) in the ms time scale. Due to the low signal to noise ratio available at low Qs and short times scales, we could not characterize neither the wave-vector dependence of the beta-relaxation nor its evolution with temperature. For this purpose, we propose here to use the large coherent flux offered by XPCS at ESRF-EBS to probe for the first time the temporal evolution of the beta-relaxation in a MG across the glass-transition temperature. A successful experiment will deepen our understanding on the glassy dynamics from an extended scale and may unveil the physical origin for the recently reported string-like atomic motions in MGs.