We report on advances using ultrahigh vacuum tip-enhanced Raman spectroscopy (UHV-TERS) to obtain vibrational information at the single molecule level, and surface enhanced-femtosecond stimulated Raman spectroscopy (SE-FSRS) to follow chemical reaction dynamics occurring near plasmonic surfaces. The combination of TERS and FSRS presents new opportunities for the study of chemistry at the space-time limit.UHV-TERS is a route toward site-specific, single-molecule spectroscopy. We resolved multiple vibrational modes for copper phthalocyanine molecules on Ag(111), obtained concurrently with molecular resolution UHV scanning tunneling microscopy. All sample preparation is performed in situ, greatly enhancing the stability of the tip-sample junction, and ensuring minimal contamination in the field enhancement region. This allows the interactions between molecular adsorbates and specific binding sites on solid surfaces to be probed with unprecedented spatial and spectroscopic resolution.SE-FSRS is a new technique which combines femtosecond Raman spectroscopy with the surface enhancement of plasmonic materials, enabling one to obtain structural snapshots of a small number of reacting molecules. We used SE-FSRS to probe the energy flow between vibrational coherences and proximal plasmons, proving that the dispersive lineshapes we observe are caused by Fano-like interactions. Interestingly, the vibrational coherences are not quenched by nearby plasmons, indicating that these molecule-plasmon couplings can be used in plasmonically-enhanced photovoltaic and photocatalytic systems. Additionally, we report on using SE-FSRS to probe excited state dynamics, as well as determining the ultimate limits of detection.

New advances in molecular plasmonics at the space-time limit

246th National Meeting (2013)

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