Extended x-ray absorption fine structure measurement of phase transformation in iron shocked by nanosecond laser

Extended x-ray absorption fine structure (EXAFS) measurements have been used to demonstrate the phase transformation from body-centered-cubic (bcc) to hexagonal-closely packed (hcp) iron due to nanosecond, laser-generated shocks. The EXAFS spectra are also used to determine the volume compression and temperature in the shocked iron, which are consistent with hydrodynamic simulations and with the compression inferred from velocity interferometric (VISAR) measurements. This is a direct, atomic-level and in situ proof of shock-induced transformation in iron. Thus, the EXAFS data can be used both for studying the phase transformation as well as for characterizing the crystal conditions (density, temperature) during the transformation. (C) 2005 American Institute of Physics.