Extracting body frame molecular geometry from ultrafast diffraction gas-phase experiments through coherent ensemble anisotropy.
ORAL
Abstract
Ultrafast electron and x-ray diffraction from molecular gases both aim to retrieve sub-picosecond and sub-nanometer intramolecular dynamics. These measurements record time-dependent pair-correlation distributions: histograms of all atomic pairwise distances in the molecule. With unlabelled distances alone, the geometry can rarely be retrieved uniquely without the aid of complex excited state dynamics simulations. Here we show a novel method that uses coherent rotational wave packets to better retrieve the molecular frame geometry. We derive a relation between the measured ensemble laboratory frame anisotropy and the molecule’s pairwise distances and molecular frame angles which otherwise remain inaccessible without extensive simulation. With this expression we retrieve the molecular geometry with both the atomic pairwise distances and the angles in the molecular frame. We do this using a monte-carlo markov chain approach that avoids the need for complex excited-state simulations. We demonstrate this method in the asymmetric top molecule NO2.
*This work is for the Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515.
–
Publication: Extracting body frame molecular geometry through coherent ensemble anisotropy in ultrafast gas-phase diffraction experiments
Extracting body frame molecular geometry in the asymmetric top NO2 through coherent ensemble anisotropy in ultrafast gas-phase diffraction experiments
Presenters
-
Kareem Hegazy
- Stanford Univ, PULSE