Extracting the Frequency-Dependent Dynamic Stokes Shift from Two-Dimensional Electronic Spectra with Prominent
Jiawei Lu1, Yumin Lee1, Jessica M Anna1
1University of Pennsylvania, 231 South 34 Street, Philadelphia, Pennsylvania 19104, United States.
The Journal of Physical Chemistry. B
|September 9, 2020
Summary
This study analyzes ultrafast solvation dynamics using dynamic Stokes shift from 2D electronic spectroscopy of cresyl violet. It reveals intramolecular vibrational modes influencing these dynamics and their excitation frequency dependence.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Computational Chemistry
Background:
- Ultrafast solvation dynamics are crucial for understanding excited-state processes.
- Dynamic Stokes shift analysis provides insights into these rapid molecular changes.
- Two-dimensional electronic spectroscopy (2DES) offers high temporal and spectral resolution.
Purpose of the Study:
- To extract and analyze the excitation frequency-dependent dynamic Stokes shift from 2DES data.
- To identify and assign intramolecular vibrational modes contributing to solvation dynamics.
- To investigate the influence of vibrational energy relaxation and spectral diffusion on observed timescales.
Main Methods:
- Acquisition and analysis of 2D electronic spectra (2DES) of cresyl violet.
- Extraction of the dynamic Stokes shift function, S(t), at various excitation frequencies.
- Utilizing Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) for vibrational mode assignment.
- Incorporating characterized vibrational oscillations into the fitting of S(t).
Main Results:
- The dynamic Stokes shift function, S(t), exhibited oscillatory behavior attributed to intramolecular vibrations.
- Excitation frequency-dependent ultrafast timescales ranging from 36 to 98 fs were determined.
- Fastest timescales were observed where contributions from vibrational relaxation and spectral diffusion were minimized.
Conclusions:
- Intramolecular vibrations play a significant role in the ultrafast solvation dynamics of cresyl violet.
- The excitation frequency dependence of the dynamic Stokes shift provides a nuanced understanding of excited-state processes.
- Optimizing 2DES analysis by minimizing contributions from other dynamic processes allows for accurate extraction of ultrafast timescales.
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