Melanie Reber
University of Georgia, GA·Chemistry·Early-career
When a molecule absorbs light, the energy it gains has to go somewhere, and the path it takes is decided in less than a trillionth of a second. A key traffic junction along that path is a conical intersection, a geometry where two electronic energy surfaces touch and the molecule can hop between them, converting light energy into vibration.
- Fields
Chemistry
Physics
- Topics
ultrafast spectroscopy
transient absorption spectroscopy
conical intersections
- Grants
- 1 known grant, through Dec 2028
What they work on
- Build ultrafast transient absorption spectroscopy inside external optical enhancement cavities, which recycle laser light through the sample, to reach the sensitivity needed to probe the low molecular densities of a molecular beam.
- Develop dual comb detection, using two frequency comb lasers, to record transient absorption spectra with quantum-state resolution so individual vibrational and rotational levels can be distinguished.
- Characterize dynamics at conical intersections in excited electronic states of small organic molecules and radicals in the gas phase, resolving the role of specific vibrations for direct comparison with theory.
- Measure conical intersections between vibrational states, such as Jahn-Teller interactions in which coupled electronic and vibrational motion distorts molecular symmetry, using visible and infrared ultrafast fiber comb lasers.
More about the research
These crossings govern photochemistry, from how pigments shed excess light energy to how molecules degrade in sunlight. Watching them cleanly is difficult: the crispest measurements come from molecules in the gas phase, in a molecular beam, where they are cold, isolated and directly comparable to theory, but such beams contain so few molecules that signals are tiny. This project develops instruments that can see ultrafast changes in absorption in these dilute samples, with fine resolution in both time and color.
Why it matters
Conical intersections control what happens to a molecule after it absorbs light, which underlies photochemistry, photostability and light-harvesting. Gas-phase measurements with both ultrafast and quantum-state resolution would give theorists sharp benchmarks for testing models of excited-state dynamics. The laser and optical-cavity techniques developed, and the training in lasers, optics and electronics, also carry over to quantum technologies and precision sensing.
Known grants
From NIH and NSF research grants. Labs often have other funding we can't see.
Closest labs
Jinjun Liu
University of Louisville, KY·Chemistry
Develop methods to produce magnesium-bearing carbon chains and clusters with odd numbers of carbon atoms, using laser ablation of magnesium with organic precursors and cooling in a supersonic molecular beam.
Shaul Mukamel
University of California-Irvine, CA·Chemistry
Develop models and computational tools to predict and interpret spectroscopy signals made with entangled photons, combining electronic structure and quantum dynamics simulations.
Patrick Vaccaro
Yale University, CT·Chemistry
Measure electronic circular birefringence of isolated, solvent-free chiral molecules using cavity ring-down polarimetry, a mirror-cavity method sensitive to tiny polarization rotations, to benchmark theoretical predictions of optical activity.
The school
University of Georgia: 27 labs on PI Pages, $628M a year on research, 598 research doctorates a year.
Reach out
A start for your email. Fill in the brackets.