Extended X-Ray Absorption Fine Structure Measurements of Laser Shocks in Ti and V and Phase Transformation in Ti

16 LLE Review, Volume 97 Introduction Recently, x-ray diffraction has been used to study dynamic material response to shocks of high pressure (~0.1 to 1 Mbar) and high strain rate (~107 to 108 s−1).1–3 The goal of this work is to demonstrate the use of extended x-ray absorption fine structure (EXAFS)4 as a complementary characterization of such laser-shocked metals. EXAFS is the modulation in the x-ray absorption above the K edge (or L edge) due to the interference of the photoelectron wave packet with the waves reflected from neighboring atoms. Unlike synchrotron experiments where the imposed temperature is known independently and the main emphasis is on the study of the chemical structure, in this experiment the emphasis is on the measurement of the compression and temperature of the shocked material through the EXAFS spectrum itself. The frequency of EXAFS modulations is related to the interparticle distance, hence to the compression. The damping rate of the modulation can yield the lattice temperature, which is not available by other methods. The assumption of three-dimensional compression, required to relate the EXAFS-determined inter-atomic distance to the density, was verified by comparison with measurements of the shock speed, which yield the compression (through the known Hugoniot equation of state).