Time-resolved x-ray diffraction of alloy formation in a AuPt multilayer film.

Revealing atomic scale motion at picosecond timescales can reveal important features of the energy landscape that dictates structure. In this work, sub-nanosecond time-resolved x-ray diffraction measurements of metallic alloy formation following sub-picosecond optical photoexcitation is presented. Under thses condtions, a Au-Pt multilayer film loses structural coherence in less than 100ps followed by the rapid growth of a new polycrystalline AuPt alloy within 1μs. Comparisons to diffusional mixing models reveals a growth rate four orders of magnitude larger than previous results would suggest.