PNNL

Abstract

XAFS (X-ray absorption fine structure) is a valuable probe of material dynamics because with it one can determine the behavior of a sample directly without dependence on long-range order, in contrast to X-ray diffraction. Dynamics of heating and phase changes induced by laser excitation may therefore be directly monitored by XAFS regardless of material state. In addition, the near-edge portion of the XAFS (the XANES—X-ray absorption near-edge spectroscopy) contains electronic information about the material and is, for example, sensitive to the shielding between the core hole and photoelectron, which can be modified by the laser pulse in a semiconductor, since the excited carrier density can be initially similar to that of a metal. The XANES technique therefore has the potential to study dynamics of this type of phenomenon, regardless of material state.