Electron Correlation Dynamics in State-Selected Triatomic Molecules Following Double Photoionization

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Electrons can be ejected from molecules when they absorb energetic photons. This can weaken the bonds and cause the molecule to dissociate into ionic fragments. Studying ionization and dissociation processes in small molecules is important for testing quantum theories and for practical reasons such as understanding radiation damage. This research studies double photoionization of water molecules in which a single photon ejects two electrons. A sophisticated measurement method is used in which the ejected electrons and the ionic fragments are detected in coincidence to determine how they share energy and in which direction they move away from each other. The details of those measurements will help theoretical physicists refine quantum mechanical models of molecules that absorb ionizing radiation. Once the basic physics is understood and included in the theoretical models, the calculations can be used to understand how radiation interacts with larger molecules and materials.The well-known COLTRIMS technique will be used to study double photoionization of water molecules with 57 eV photons. The initial momenta of the photoelectrons and ionic fragments will be determined. In addition, the dication molecular state will be characterized prior to dissociation. The data analysis methods will also be able to project the electrons' momenta into the frame of the dissociated molecule. As a result, state-selected, body-fixed differential cross sections for the coupled photoelectrons can be determined, achieving as-yet unprecedented knowledge of the dissociating molecule.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.