Imaging valence electron structural rearrangement in ammonia using hard x-ray scattering

ORAL

Abstract

We report here the observation of the hard x-ray scattering signature of valence electron rearrangement in photoexcited ammonia. While ultrafast hard x-ray scattering has been a powerful tool for imaging structural rearrangement in molecules, it has historically been used primarily to track the motion of the atomic centers. The dominant contribution to the structural information encoded in the total scattering signal usually originates from the tightly bound core electrons around each atom, allowing one to neglect valence electron structure and utilize the independent atom model approximation. We performed an ultrafast hard x-ray scattering experiment to investigate the extent to which valence electron rearrangement contributes to the scattering signal. Gas-phase deuterated ammonia, ND3, was photoexcited with a 200 nm pump pulse to a 3s Rydberg state and probed with a 10 keV x-ray pulse with sufficient time resolution to observe scattering changes due to the initial photoexcitation, umbrella unbending motion, and subsequent deuterium dissociation dynamics. The use of ultrafast hard x-ray scattering to image the structural rearrangement of single valence electrons constitutes an important advance in the experimental techniques used to study ultrafast photochemistry.

*I.G., P.H.B. and A.M.G. were supported by the National Science Foundation. This work was supported by the AMOS program within the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. Use of the Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. N.H.L. acknowledges start-up funding from the School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), KTH Royal Institute of Technology.

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Presenters

  • Ian Gabalski

    • Stanford Univ
    • Stanford University

Authors

  • Ian Gabalski

    • Stanford Univ
    • Stanford University

  • Alice Green

    • Stanford PULSE Institute
    • SLAC National Accelerator Laboratory

  • Philipp Lenzen

    • SLAC National Accelerator Laboratory

  • Felix Allum

    • Stanford University

  • Matthew Bain

    • SLAC National Accelerator Laboratory

  • Surjendu Bhattacharyya

    • Kansas State University
    • SLAC National Accelerator Laboratory
    • J.R. Macdonald Laboratory, Kansas State University, Manhattan, KS, USA

  • Mathew Britton

    • Stanford University

  • xinxin Cheng

    • SLAC National Accelerator Laboratory
    • SLAC National Acccelerator Laboratory

  • James P Cryan

    • SLAC National Accelerator Laboratory

  • Taran Driver

    • SLAC

  • Ruaridh Forbes

    • SLAC National Accelerator Laboratory

  • Aaron M Ghrist

    • Stanford University

  • Martin Grassl

    • SLAC National Accelerator Laboratory

  • Kirk Larsen

    • SLAC National Accelerator Laboratory

  • Mengning Liang

    • Linac Coherent Light Source, SLAC National Accelerator Laboratory

  • Ming-Fu Lin

    • SLAC - Natl Accelerator Lab
    • SLAC National Accelerator Laboratory

  • Yusong Liu

    • SLAC National Laboratory

  • Michael P Minitti

    • SLAC National Accelerator Laboratory

  • Silke Nelson

    • SLAC National Accelerator Laboratory

  • Joseph S Robinson

    • SLAC National Accelerator Laboratory

  • Nanna H List

    • KTH Royal Institute of Technology

  • Philip H Bucksbaum

    • Stanford Univ
    • Stanford University

  • Thomas J Wolf

    • SLAC National Accelerator Laboratory

  • James M Glownia

    • SLAC - Natl Accelerator Lab
    • SLAC National Accelerator Laboratory