Loomis Group at WashU

Our research endeavors focus on the detailed interrogation and manipulation of reaction dynamics at the molecular and atomic level. Current thrusts include the investigation of quantum-confinement effects in one-dimensional semiconductor nanostructures and their utility for light to electrical conversion and charge-transport and the spectroscopic characterization of intermolecular interactions and bimolecular reaction dynamics.

While the push toward faster and more efficient electronic circuitry relies on the ability to synthesize semiconductor structures on nanometer scales, the optical and electronic properties of these nanostructures are interesting in their own right. We are investigating quantum effects that arise from the reduced dimensionality of semiconductor nanodots, nanowires, and nanoplatelets using absorption and fluorescence spectroscopy. Our group is also developing novel optical microscopy experiments that will enable us to use multiple femtosecond lasers to excite and monitor the dynamics of excitons in and along single nanostructures with temporal and spatial resolution.

The techniques implemented to investigate intermolecular interactions include femtosecond to nanosecond time scales, linear and non-linear laser spectroscopy, quantum-mechanical wave packet dynamics and coherent control, and intramolecular and intermolecular energy redistribution. Molecular beam and supersonic expansion techniques are used to lower the internal energies of molecules and to form weakly bound pre-reactive complexes. These complexes represent the launching pad for the subsequent intermolecular dynamics experiments. The experiments utilize numerous fluorescence-based spectroscopies and ion time-of-flight mass spectrometry and ion velocity-map-imaging techniques to fully map the identities and energetics of the parents and products. Past experiments have focused on characterizing the interactions of and dynamics between rare gas atoms or molecular hydrogen with dihalogen molecules. Current experiments are centered on charge transfer complexes, including I₂, Br₂, or NO⁺ with C₂H₄ or C₆H₆.

While our research efforts are generally categorized as Physical Chemistry or Chemical Physics, postdocs, graduate students, and undergraduate students with an array of skills and interests have made significant contributions to these efforts. The experiments utilize an array of tools, including nanosecond and femtosecond lasers, ultrashort pulse shaping, mass spectrometry and ion imaging, absorption and fluorescence spectroscopy, as well as confocal microscopy. Thus, hardworking individuals who have a strong foundation in Physical Chemistry, Materials Chemistry, and Spectroscopy coupled with good problem-solving skills and interactive personalities do well in our group.