Rapid-Scan Resonant Two-Dimensional Impulsive Stimulated Raman Spectroscopy of Excited States
Journal of Physical Chemistry A, 2023, Volume 127, pp. 5276-5286.
Photochemical reactions occur in the electronically excitedstate,which is effectively represented by a multidimensional potential energysurface (PES) with a vast degree of freedom of nuclear coordinates.The elucidation of the intricate shape of the PES constitutes an importanttopic in the field of photochemistry and has long been studied bothexperimentally and theoretically. Recently, fully time-domain resonanttwo-dimensional Raman spectroscopy has emerged as a potentially powerfultool to provide unique information about the coupling between vibrationalmanifolds in the excited state. However, the wide application of thistechnique has been significantly hampered by the technical difficultiesassociated with experimental implementation and remains challenging.Herein, we demonstrate time-domain resonant two-dimensional impulsivestimulated Raman spectroscopy (2D-ISRS) of excited states using sub-10fs pulses based on the rapid scan of the time delay, which facilitatesthe efficient collection of time-domain vibrational signals with highsensitivity. As a proof-of-principle experiment, we performed 2D-ISRSof 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) insolution. Through 2D Fourier transformation of the high-quality time-timeoscillatory signal, we obtained a 2D frequency-frequency correlationmap of excited-state TIPS-pentacene in the broad frequency windowof 0-2000 cm(-1). The data clearly resolvea number of cross peaks that signify the correlations among excited-statevibrational manifolds. The high capability of the rapid-scan-based2D-ISRS spectrometer presented in this study enables the systematicinvestigation of various photochemical reaction systems, thereby furtherpromoting the understanding and applications of this new multidimensionalspectroscopy.
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