Seminars Archive

Time-Resolved X-ray Laser Induced Photoelectron Spectroscopy for Probing Materials Dynamics

Abstract


Monday, July 18, 2005, 11:00


Seminar Room

Sincrotrone Trieste, Basovizza
Time-Resolved X-ray Laser Induced Photoelectron Spectroscopy for Probing Materials Dynamics


A.J. Nelson

(Lawrence Livermore National Laboratory, Livermore, CA 94551)
Abstract
Time-resolved x-ray photoelectron spectroscopy is used to probe the non-steady-state evolution of the valence band electronic structure of laser heated ultra-thin (50 nm) Cu. Single-shot x-ray laser induced time-of-flight photoelectron spectroscopy with picosecond time resolution is used in conjunction with optical measurements of the disassembly dynamics that have shown the existence of a metastable liquid phase in fs-laser heated Cu foils persisting 4-5 ps. This metastable phase is created using a 527 nm wavelength 400 fs laser pulse containing 0.1 - 2.5 mJ laser energy focused in a large 500 x 700 m2 spot to induce isochoric heating of the Cu under conditions of 0.07 - 1.8 x 1012 W cm-2 intensity. Valence band photoemission spectra showing the changing occupancy of the Cu 3d level with heating are presented. These are the first picosecond x-ray laser time-resolved photoemission spectra of laser-heated ultra-thin Cu foil showing changes in electronic structure. The ultrafast nature of this technique lends itself to true single-state measurements of shocked and heated materials. This work was performed under the auspices of the U.S. Dept. of Energy by the University of California Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.