Laser spectroscopy allows scientists to probe the dynamics and properties of the materials — both biological and synthetic. As we develop new ways to probe these systems, we learn more about how to design and control the dynamics required to generate new functional materials.
Nonlinear spectroscopic methods probe dynamics on the timescale of femtoseconds -- millionths of a billionth of a second. Two-dimensional electronic spectra allow us to inspect directly how excited states are coupled to one another, how they relax, and how they trade energy.
After many sleepless nights in the lab collecting data, we recently developed a new approach to acquiring 2D-electronic spectra that utilizes spatiotemporal gradients in direct analogy to the quantum mechanics of Magnetic Resonance Imaging (MRI). This new tool allows us to probe systems 300x faster with 50x better signal-to-noise ratio.
The spectra that we acquire contain information about how states couple to one another as a function of time. The Fourier transform of coherent beating signals allows us to create 3D representations of our data and directly extract parameters from the underlying Hamiltonian.
L. Wang*, M.A. Allodi* and G.S. Engel, "Quantum coherences reveal excited state dynamics in biophysical systems" Nat. Rev. Chem. 3 477–490 2019.
J. Otto, L. Wang, I. Pochorovski, S.M. Blau, A. Aspuru-Guzik, Z. Bao, G.S. Engel, and M. Chiu, "Disentanglement of Excited-State Dynamics with Implications for FRET Measurements: Two-Dimensional Electronic Spectroscopy of a BODIPY-Functionalized Cavitand" Chemical Science 9, 3694-3703 2018.