48th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 62, Number 8
Monday–Friday, June 5–9, 2017;
Sacramento, California
Session H7: Focus Session: Ultrafast and Nonlinear Xray Processes
10:30 AM–12:30 PM,
Wednesday, June 7, 2017
Room: 313
Chair: Gilles Doumy, Argonne National Laboratory
Abstract ID: BAPS.2017.DAMOP.H7.1
Abstract: H7.00001 : Coherent Multidimensional Core Spectroscopy of Molecules with Multiple X-ray pulses
10:30 AM–11:00 AM
Preview Abstract
Abstract
Author:
Shaul Mukamel
(University of California, Irvine)
Multidimensional spectroscopy uses sequences of optical pulses to study
dynamical processes in complex molecules through correlation plots involving
several time delay periods. Extensions of these techniques to the x-ray
regime will be discussed. Ultrafast nonlinear x-ray spectroscopy is made
possible by newly developed free electron laser and high harmonic generation
sources. The attosecond duration of X-ray pulses and the atomic selectivity
of core X-ray excitations offer a uniquely high spatial and temporal
resolution. We demonstrate how stimulated Raman detection of an X-ray probe
may be used to monitor the phase and dynamics of the nonequilibrium valence
electronic state wavepacket created by e.g. photoexcitation, photoionization
and Auger processes. Spectroscopy of multiplecore excitations provides a new
window into electron correlations. Applications will be presented to
long-range charge transfer in proteins and to excitation energy transfer in
porphyrin arrays. Conical intersections (CoIn) dominate the pathways and
outcomes of virtually all photophysical and photochemical molecular
processes. Despite extensive experimental and theoretical effort CoIns have
not been directly observed yet and the experimental evidence is being
inferred from fast reaction rates and some vibrational signatures. Novel
ultrafast X ray probes for these processes will be presented. Short X-ray
pulses can directly detect the passage through a CoIn with the adequate
temporal and spectral sensitivity. The technique is based on a coherent
Raman process that employs a composite femtosecond/attosecond X-ray pulse to
directly detect the electronic coherences (rather than populations) that are
generated as the system passes through the CoIn. Streaking of time-resolved
photoelectron spectroscopy (TRPES) signals offers another powerful window
into the joint electronic/vibrational dynamics at concial intersections.
Strong coupling of molecules to the vacuum field of micro cavities can
modify the potential energy surfaces thereby manipulating the photophysical and photochemical
reaction pathways. The photonic vacuum state of a localized cavity mode can
be strongly mixed with the molecular degrees of freedom to create hybrid
field-matter states known as polaritons. Simulations of the avoided crossing
of sodium iodide in a cavity which incorporate the quantized cavity field
into the nuclear wave packet dynamics will be presented. Numerical results
show how the branching ratio between the covalent and ionic dissociation
channels can be strongly manipulated by the optical cavity.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2017.DAMOP.H7.1