Moniruzzaman Shaikh, LBNL

Abstract

Probing electron correlation in ethylene molecules by direct photo double ionization

M. Shaikh1, W. Iskandar1, S. Lee1, Frank L. Yip2, Robert R. Lucchese1, C. William McCurdy1,3, D. S. Slaughter1, and Th. Weber1

1 Lawrence Berkeley National Laboratory, Chemical Sciences Division, 1 Cyclotron Road, Berkeley, CA-94720, USA,
2 Department of Science and Mathematics, California State University-Maritime Academy, Vallejo, California 94590, USA
3 Department of Chemistry, University of California, Davis, California 95616, USA

Direct photo double ionization (PDI) of an atom or molecule by a single photon is an ideal testbed for investigating electron-electron correlation. Previous experimental investigations on simple hydrogen molecules over 20 years ago demonstrated that highly differential cross sections such as the relative electron emission angle in the body fixed frame with respect to the polarization vector can be measured [1, 2] and reproduced by ab initio calculations. Applying this approach to a polyatomic molecule provides the opportunity to better understand the interplay between electronic correlations within the molecule. Here, we investigated the PDI of single ethylene molecules near the double ionization threshold, in order to unravel the fundamental physics of electron correlation in inter-shell and intra-shell dielectron emissions and the subsequent molecular dynamics.

We used XUV photons (40.5 eV) from the Advanced Light Source and employed COLd Target Recoil Ion Momentum Spectroscopy (COLTRIMS) in order to detect the two ejected electrons and related photo-fragments in coincidence for three different dissociation channels: symmetric breakup, deprotonation, and hydrogen elimination. In this presentation, electron-ion and electron-electron energy correlation maps, along with molecular frame photoelectron angular distributions for the three different fragmentation channels and select electron energy-sharing scenarios, will be presented and compared.

Double core ionization probes the bonding properties very sensitively [3, 4], as, for example, the chemical shift of double core- hole states (involving atoms of the same species in a larger molecule, e.g., ethylene). Using LCLS-II and the DREAM end-station, we plan to extend our approach and probe the electron-electron correlation for the core electrons, and the subsequent molecular dissociation.