Finite temperature full multiple scattering calculation of ultrafast x-ray absorption spectroscopy*

Recent advances in ultrafast time-resolved (TR) x-ray absorption spectroscopy (XAS) have allowed us to probe the interaction between electronic temperature (T_e) and lattice temperature (T_i) on the femtosecond time-scale. We present a finite temperature multiple scattering Green's function calculations of XAS, which accounts for the finite T_e of the system, to describe these extreme conditions. The effect of temperature on lattice can be included at different levels of approximation such as using correlated Debye (CD) model or dynamical matrix. We apply the method to TR-XANES of an Fe-MgO layered hetero-structure [1] and a copper system [2]. We are able to qualitatively reproduce the experimental results with FEFF using CD model. We also obtain estimates of T_e based on a shift in the edge and T_i based on the size of the Debye-Waller factor.

[1] Rothenbach et al. Microscopic non-equilibrium energy transfer dynamics in a photoexcited metal/insulator heterostructure. PhysRevB (to be published)

[2] Cho et al. Electronic Structure of Warm Dense Copper Studied by Ultrafast X-Ray Absorption Spectroscopy. PhysRevLett.106.167601