Ultrafast time resolved x-ray diffraction, extended x-ray absorption fine structure and x-ray absorption near edge structure

Ali Oguz Er,Jie Chen,Peter M Rentzepis

doi:10.1063/1.4738372

Abstract

Ultrafast time resolved x-ray absorption and x-ray diffraction have made it possible to measure, in real time, transient phenomena structures and processes induced by optical femtosecond pulses. To illustrate the power of these experimental methods, we present several representative examples from the literature. (I) Time resolved measurements of photon/electron coupling, electron/phonon interaction, pressure wave formation, melting and recrystallization by means of time resolved x-ray diffraction. (II) Ultrafast x-ray absorption, EXAFS, for the direct measurement of the structures and their kinetics, evolved during electron transfer within molecules in liquid phase. (III) XANES experiments that measure directly pathway for the population of high spin states and the study of the operating mechanism of dye activated TiO2 solar cell devices. The construction and use of novel polycapillary x-ray lenses that focus and collimate hard x-rays efficiently are described.

Highlights

Title Ultrafast time resolved x-ray diffraction, extended x-ray absorption fine structure and x-ray absorption near edge structure
To illustrate the power of these experimental methods, we present several representative examples from the literature. (I) Time resolved measurements of photon/electron coupling, electron/phonon interaction, pressure wave formation, melting and recrystallization by means of time resolved x-ray diffraction. (II) Ultrafast x-ray absorption, extended x-ray absorption fine spectroscopy (EXAFS), for the direct measurement of the structures and their kinetics, evolved during electron transfer within molecules in liquid phase. (III) X-ray near edge structure (XANES) experiments that measure directly pathway for the population of high spin states and the study of the operating mechanism of dye activated TiO2 solar cell devices
Ultrafast time-resolved EXAFS imaging techniques have been employed to study the dynamics of the femtosecond laser ablation of aluminum in an energy range well above the ablation threshold

Summary

Introduction

Title Ultrafast time resolved x-ray diffraction, extended x-ray absorption fine structure and x-ray absorption near edge structure. Ultrafast time resolved x-ray absorption and x-ray diffraction have made it possible to measure, in real time, transient phenomena structures and processes induced by optical femtosecond pulses. Ultrafast time-resolved EXAFS imaging techniques have been employed to study the dynamics of the femtosecond laser ablation of aluminum in an energy range well above the ablation threshold They have shown that photomechanical fragmentation and vaporization were the dominant mechanisms for the production of liquid nanoparticles and neutral atoms.. Electron transfer in iron and cobalt liquid complexes, in solution, has been studied using time resolved EXAFS with subpicosecond and sub-Angstrom resolution.17,18 These studies determined that the mechanism of the electron transfer processes, initiated by photo-excitation in the charge transfer band, can be either intra or intermolecular depending on the structure of the molecule and degree of freedom of rotation of the ligand. Several electron and x-ray ultrafast time resolved experiments have reported on the transient changes in the lattice structure of single crystals after excitation with an fs optical pulse.

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