Time-resolved Sum-Frequency Generation (SFG) data for vibrational dephasing: These data derive from ultrafast pump-probe measurements on single plasmonic nanogaps. The dataset includes spectro-temporal maps and the extracted decay curves of the coherent vibrational signal from the NO₂ stretch mode of nitrothiophenol (NTP) molecules. Data are provided for individual nanoparticle-on-resonator (NPoR) structures.

Vibrational coherence beating data from dipole-dipole coupling: These data capture the oscillatory modulation of the SFG signal, resulting from the interference between symmetric and antisymmetric collective vibrational modes. The dataset includes the extracted beating frequencies and the corresponding fits used to determine the intermolecular dipole coupling strength (ΔΩ).

Dephasing time (T₂) distributions for pure and mixed self-assembled monolayers (SAMs): These data comprise the measured coherence lifetimes for the nitrostretch vibration under varying molecular packing densities. The dataset includes results for pure NTP SAMs and for SAMs where NTP is diluted with the spacer molecule 1,1'-biphenol-4-thiol (BPT) at specific fractional coverages (xₙ).

Continuous-Wave Surface-Enhanced Raman Spectroscopy (CW-SERS) data for coverage calibration: These data consist of Raman spectra used to determine the fractional surface coverage (xₙ) of molecules within the nanogaps. The dataset includes spectra showing the intensity ratios of characteristic NTP and BPT ring modes, as well as the spectral blueshift of the coupled NO₂ vibration with increasing packing density.

BPT control data for cavity-dominated dephasing: These data consist of the time-resolved SFG measurements and extracted dephasing times for the weakly-coupled ring vibration of BPT-only SAMs. This dataset provides a comparison for the dephasing behavior in the regime where cavity interactions dominate over intermolecular coupling.