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TD-DFT Calculations of One- and Two-Photon Absorption in Coumarin C153 and Prodan: Attuning Theory to Experiment

Abstract

We use TD-DFT to calculate the one-photon absorption (1PA) and two-photon absorption (2PA) properties of C153 and Prodan in toluene and DMSO, and benchmark different methods relative to accurate experimental data available from literature on these particular systems. As the first step, we modify the range-separated TD-DFT to provide the best prediction for the peak 1PA wavelength, and then apply the optimized functionals to achieve quantitative predictions of the corresponding two-photon absorption cross section, σ2PA, with an accuracy ~10-20 % in C153 and ~20-30% in Prodan. To elucidate the origin of residual discrepancies between the theory and experimental observations, we invoked the two essential states model for σ2PA, which allows us to verify not only the transition wavelength and the σ2PA value, but also to quantitatively benchmark calculation of key molecular parameters such as the transition dipole moment and the change of permanent dipole moment. Such comprehensive cross-checking indicates that a larger discrepancy in Prodan is most likely caused by a noted failure of DFT to predict the relative intensity and relative ordering of closely lying excited states with different degree of intramolecular charge transfer, which we further support by analyzing the predictions obtained by high-level coupled-cluster calculations in gas phase. Our results highlight the utility of benchmarking the calculations not only relative to other theoretical methods, but also in comparison to the experimental measurements, wherever such data is available.

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Publication details

The article was received on 13 Jul 2017, accepted on 29 Sep 2017 and first published on 02 Oct 2017


Article type: Paper
DOI: 10.1039/C7CP04735E
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    TD-DFT Calculations of One- and Two-Photon Absorption in Coumarin C153 and Prodan: Attuning Theory to Experiment

    M. Uudsemaa, A. Trummal, S. de Reguardati, P. Callis and A. Rebane, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP04735E

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