Visualizing electron rearrangement in space and time during the transition from a molecule to atoms

Imaging and controlling reactions in molecules and materials at the level of electrons is a grand challenge in science, relevant to our understanding of charge transfer processes in chemistry, physics, and biology, as well as material dynamics. Direct access to the dynamic electron density as electr...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2010-11, Vol.107 (47), p.20219-20222
Main Authors: Li, Wen, Jaroń-Becker, Agnieszka A., Hogle, Craig W., Sharma, Vandana, Zhou, Xibin, Becker, Andreas, Kapteyn, Henry C., Murnane, Margaret M.
Format: Article
Language:English
Subjects:
Angular distribution
Atoms
Atoms & subatomic particles
Bromine
Chemical bonds
Electron density
Electrons
Elementary Particle Interactions
Ionization
Ions
Kinetic energy
Kinetics
Lasers
Molecular chemistry
Molecular Dynamics Simulation
Molecular orbitals
Molecules
Photoelectron Spectroscopy - methods
Physical Sciences
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Summary:Imaging and controlling reactions in molecules and materials at the level of electrons is a grand challenge in science, relevant to our understanding of charge transfer processes in chemistry, physics, and biology, as well as material dynamics. Direct access to the dynamic electron density as electrons are shared or transferred between atoms in a chemical bond would greatly improve our understanding of molecular bonding and structure. Using reaction microscope techniques, we show that we can capture how the entire valence shell electron density in a molecule rearranges, from molecular-like to atomic-like, as a bond breaks. An intense ultra-short laser pulse is used to ionize a bromine molecule at different times during dissociation, and we measure the total ionization signal and the angular distribution of the ionization yield. Using this technique, we can observe density changes over a surprisingly long time and distance, allowing us to see that the electrons do not localize onto the individual Br atoms until the fragments are far apart (∼5.5 Å), in a region where the potential energy curves for the dissociation are nearly degenerate. Our observations agree well with calculations of the strong-field ionization rates of the bromine molecule.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1014723107