Virtual Winter School on Computational Chemistry

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Transition dipole moment

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

    Speaker: Assistant Professor Samer Gozem
    Institute: Georgia State University
    Country: USA
    Speaker Link:
    Time: 19:00 CET 21-Feb-22

    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).


    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    has not been peer-reviewed.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.