Prediction of Fluorescence Quantum Yields using the Extended Thawed Gaussian Approximation

Abstract

Spontaneous emission and internal conversion rates are calculated within harmonic approximations and compared to results obtained within the semi-classical extended thawed Gaussian approximation. This is the first application of the ETGA in the calculation of internal conversion and emission rates for real molecular systems, namely formaldehyde, fluorobenzene, azulene and a dicyano-squaraine dye. The viability of the models as black-box tools for prediction of spontaneous emission and internal conversion rates is assessed. All calculations were done using a consistent protocol in order to investigate how different methods perform without previous experimental knowledge. Contrasting the results with experimental data shows that there are further improvements required before theoretical predictions of emission and internal conversion rates can be used as reliable indicator for the photo-luminescence properties of molecules. We find that the extended thawed Gaussian approximation performs rather similar to the vertical harmonical model. Including anharmonicities in the calculation of internal conversion rates has a moderate effect on the quantitative results in the studied systems. The electronic structure calculations were done using the B3LYP, PBE0, $\omega$B97XD and CAM-B3LYP functionals. The choice of the functional does not appear to be a major limiting factor for a black-box approach, when it comes to the prediction of radiative and nonradiative rates for organic molecules. The emission rates are fairly stable with respect to computational parameters, but the internal conversion rate reveals itself to be highly dependent on the choice of the spectral lineshape function, particularly the width of the Lorentzian function, associated with homogeneous broadening.

References in corpus (9)

• Computing quantum dynamics in the semiclassical regime
• On-the-fly ab initio semiclassical evaluation of absorption spectra of polyatomic molecules beyond the Condon approximation
• Single-Hessian thawed Gaussian approximation: The missing rung on the ladder
• Semiclassical Approach to Photophysics Beyond Kasha's Rule and Vibronic Spectroscopy Beyond the Condon Approximation. The Case of Azulene
• On-the-fly ab initio semiclassical evaluation of vibronic spectra at finite temperature
• Finite-temperature, anharmonicity, and Duschinsky effects on the two-dimensional electronic spectra from ab initio thermo-field Gaussian wavepacket dynamics
• On-the-fly ab initio three thawed Gaussians approximation: A semiclassical approach to Herzberg-Teller spectra
• Nonadiabatic instanton rate theory beyond the golden-rule limit
• Internal Conversion Rates from the Extended Thawed Gaussian Approximation: Theory and Validation

Cited by in corpus (3)

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