Two-dimensional electronic-vibrational sum frequency spectroscopy for interactions of electronic and nuclear motions at interfaces.
basic_science · Level V
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- Record sourced from PubMed, PMID 34417312.
- Also identified by DOI 10.1073/pnas.2100608118 and PMC identifier 8403924.
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Abstract
Interactions of electronic and vibrational degrees of freedom are essential for understanding excited-states relaxation pathways of molecular systems at interfaces and surfaces. Here, we present the development of interface-specific two-dimensional electronic-vibrational sum frequency generation (2D-EVSFG) spectroscopy for electronic-vibrational couplings for excited states at interfaces and surfaces. We demonstrate this 2D-EVSFG technique by investigating photoexcited interface-active (<i>E</i>)-4-((4-(dihexylamino) phenyl)diazinyl)-1-methylpyridin-1- lum (AP3) molecules at the air-water interface as an example. Our 2D-EVSFG experiments show strong vibronic couplings of interfacial AP3 molecules upon photoexcitation and subsequent relaxation of a locally excited (LE) state. Time-dependent 2D-EVSFG experiments indicate that the relaxation of the LE state, <i>S</i><sub>2</sub>, is strongly coupled with two high-frequency modes of 1,529.1 and 1,568.1 cm<sup>-1</sup> Quantum chemistry calculations further verify that the strong vibronic couplings of the two vibrations promote the transition from the <i>S</i><sub>2</sub> state to the lower excited state <i>S</i><sub>1</sub> We believe that this development of 2D-EVSFG opens up an avenue of understanding excited-state dynamics related to interfaces and surfaces.