Spectroscopy in the Gas and Condensed Phase: Bridging Theory and Experiments

Professor Samer Gozem

Department of Chemistry, Georgia State University, Atlanta, GA 30303, USA

UV-visible and photoelectron spectroscopy are powerful tools for probing the structure of
matter from the subatomic to the bulk scale. The experimental spectra are generally
plotted using two properties: energies and absorption strength (the latter typically reported
as molar attenuation coefficients or cross sections). Energies and transition strengths
could also be predicted from first principles with quantum chemical methods. In the gas
phase, experiments and computations can be reconciled when the appropriate quantum
chemical methods are used. In the condensed phase, however, experimental spectra are
shifted and broadened by intermolecular interactions that complicate the comparison
between theory and computations. At the same time, the condensed-phase spectra
encode potential important information about these intermolecular interactions and how
they modulate a solute’s electronic structure. The first part of the presentation will cover
the basics of computational spectroscopy, and discuss how computed energies and
intensities can be compared with experimental ones. The second part of the presentation
will bring the computations into the condensed phase with hybrid quantum chemical /
molecular mechanical (QM/MM) models, which can be used to understand the effect of a
solvent (or a protein host) on the spectroscopic properties of a solute (or cofactor).

Recording:

Video is available only for registered users.

References:

1. Gozem, S.; Krylov, A.I. The ezSpectra suite: An easy‐to‐use toolkit for
spectroscopy modeling. WIREs Comp. Mol. Sci. e1546. 2021.
2. Tarleton, A.; Garcia-Alvarez, J.; Wynn, A.; Awbrey, C.; Roberts, T.; Gozem, S.
OS100: A Benchmark Set of 100 Digitized UV-Visible Spectra and Derived
Experimental Oscillator Strengths. ChemRxiv 2021. This content is a preprint and
has not been peer-reviewed.
3. Dratch, B.D.; Orozco-Gonzalez, Y.; Gadda, G.; Gozem, S. The Ionic Atmosphere
Effect on the Absorption Spectrum of a Flavoprotein: A Reminder to Consider
Solution Ions. J. Phys. Chem. Lett. 12 (34), 8384–8396. 2021.
4. Orozco-Gonzalez, Y.; Kabir, M.P.; Gozem, S. Electrostatic Spectral Tuning Maps
for Biological Chromophores. J. Phys. Chem. B. 148, 4813—4824. 2019.