Nanoscale depth resolution of lattice dynamics

We employ grazing-incidence femtosecond x-ray diffraction to characterize the coherent, femtosecond laser-induced lattice motion of a bismuth crystal as a function of depth from the surface with a temporal resolution of ~200 fs. The data show direct consequences on the lattice motion from carrier diffusion and electron-hole interaction, allowing us to estimate the effective diffusion rate for the highly excited carriers and the electron-hole interaction time.