Laser driven solid-state diffusional mixing in a Ni-Pt multilayer film probed by hard x-ray diffraction*

Intense optical excitation has been utilized for decades to modify atomic scale structure in the condensed phase. When the optically excited systems are probed by hard x-ray radiation, one can reconstruct the modified atomic structure on a sub-angstrom spatial scale. In this work we utilize sub-picosecond optical radiation to rapidly drive atomic diffusion in a Ni-Pt multilayer film. Transient atomic diffusion was measured using hard x-ray diffraction, thereby directly observing the formation of a new metallic alloy as a function of laser excitation. Our observations demonstrate that the diffusional mixing in the multilayer can be completed in only a few individual laser shots, allowing us to directly probe the dynamics of the atomic scale motion.