X-ray movies of ultrafast atomic motion Barty, C.P.J.; Siders, C.W.; Cavalleri, A. ...
1999 IEEE LEOS Annual Meeting Conference Proceedings. LEOS'99. 12th Annual Meeting. IEEE Lasers and Electro-Optics Society 1999 Annual Meeting (Cat. No.99CH37009),
1999, Letnik:
1
Conference Proceeding
Using ultrafast-X-ray, line radiation generated with a 20-fs multi-terawatt laser system, we are able to observe femtosecond-laser-induced lattice dynamics in bulk semiconductors with milliangstrom ...spatial and picosecond temporal resolution via time resolved X-ray diffraction. Coherent phonon generation and propagation, ultrafast melting of thin films and buried interface lattice coupling have been observed.
Summary form only given. We present the first optical-pump X-ray probe study on coherent lattice dynamics in semiconductor heterostructures. We have observed propagation of optically generated ...picosecond acoustic pulses within crystalline Ge films and into the underlying Si substrate, where 20 femtometer lattice compression was observed.
The first soft X-ray free-electron laser has recently been put into operation at DESY in Hamburg. Tunable soft X-ray coherent radiation can be generated at the FLASH (Free-electron LASer in Hamburg; ...formerly known as VUV FEL or TTF2 FEL). In the interaction experiments reported here, the laser system provided ~ 25-fs, ~ 10-μ J pulses of 32-nm radiation. We irradiated thin (500 nm) layers of poly (methyl methacrylate) – PMMA deposited on a silicon substrate by single, focused FLASH pulses. The pulse energy was adjusted using a gas attenuator.
Results are presented of initial experiments on the interaction of ultrashort high intensity XUV pulses with solids, carried out at the XUV free electron laser facility FLASH at DESY (Hamburg).
Light-matter interaction at the nanoscale in magnetic alloys and heterostructures is a topic of intense research in view of potential applications in high-density magnetic recording. While the ...element-specific dynamics of electron spins is directly accessible to resonant x-ray pulses with femtosecond time structure, the possible element-specific atomic motion remains largely unexplored. We use ultrafast electron diffraction to probe the temporal evolution of lattice Bragg peaks of FePt nanoparticles embedded in a carbon matrix following excitation by an optical femtosecond laser pulse. The diffraction interference between Fe and Pt sublattices enables us to demonstrate that the Fe mean-square vibration amplitudes are significantly larger that those of Pt as expected from their different atomic mass. Both are found to increase as energy is transferred from the laser-excited electrons to the lattice. Contrary to this intuitive behavior, we observe a laser-induced lattice expansion that is larger for Pt than for Fe atoms during the first picosecond after laser excitation. This effect points to the strain-wave driven lattice expansion with the longitudinal acoustic Pt motion dominating that of Fe.
