Advancements in Surface-Enhanced Femtosecond Stimulated Raman Spectroscopy: Exploring Factors Influencing Detectability and Shapes of Spectra

The combination of femtosecond stimulated Raman scattering (FSRS) ability to capture fast vibrational dynamics with surface-enhanced Raman scattering (SERS) detection capabilities at low concentrations facilitated by surface plasmon resonances, was proposed as a new method of amplifying Raman signals, aiming to leverage the temporal precision of FSRS and the sensitivity of SERS for advanced molecular dynamics analysis. Within that idea's first few successful implementations, unexpected spectral distortions – mainly Fano-like dispersive shapes of bands – were observed, for which a few explanations were proposed. Further progress of this novel technique and its wider implementation requires a profound understanding of factors influencing the shape of registered spectra and the mechanism behind them. Here, we present findings on how factors such as pulse energy and excitation wavelengths impact the surface-enhanced femtosecond stimulated Raman spectroscopy (SE-FSRS) spectra, noting the influence of a strong broadband background on spectral dispersion. Our work contributes to understanding the complex mechanisms behind SE-FSRS and suggests methods for improving control and application of this spectroscopic technique, highlighting its potential for providing deeper insights into molecular dynamics. This research marks a significant step toward exploiting SE-FSRS for advanced analytical applications, including rapid detection for chemical sensing and detailed studies at the single-molecule level. This work offers new insights into the mechanisms of SE-FSRS and aids in optimising experimental conditions.