Andrea Cavalleri

Abstract:

Femtosecond x-rays were for the first time used to probe a photo-induced solid-solid phase transition in VO2. The fast timescale observed suggests that, in this regime, the structural distortion may not be thermally initiated.

Abstract:

Ultrafast optical-pump, x-ray diffraction probe experiments are providing new ways to study transient processes in physics, chemistry, and biology. In addition, the direct observation of the atomic motion by which many solid-state processes and chemical and biochemical reaction take place is included as well. As such, current table-top-terawatt femtosecond laser systems provide an attractive source of few-hundred femtosecond duration bursts of angstrom-scale x-ray radiation with fluxes comparable to standard rotating-anode sources.

Abstract:

Time-resolved x-ray diffraction with sub-300 fs, multi-keV x-ray pulses was used to study ultrafast lattice dynamics in laser-irradiated germanium and bismuth. In bismuth strong excitation of optical phonons is observed prior to disordering of the material.

Abstract:

Femtosecond X-ray diffraction of short-pulse irradiated semiconductors was discussed. Ultrafast non-thermal solid-to-liquid transition in thin single-crystal Ge-111 films grown on Si-111 substrates were also studied. Proposed 4^th generation light sources based upon single-pass x-ray free-electron lasers permitted single-shot structural determination of complex biomolecules.