The absolute Raman scattering cross section (σ RS ) for the 1584-cm −1 band of benzenethiol at 897 nm (1.383 eV) has been measured to be 8.9 ± 1.8 × 10 −30 cm 2 using a 785-nm pump laser. A temperature-controlled, small-cavity blackbody source was used to calibrate the signal output of the Raman spectrometer. We also measured the absolute surface-enhanced Raman scattering cross section (σ SERS ) of benzenethiol adsorbed onto a silver-coated, femtosecond laser-nanostructured substrate. Using the measured values of 8.9 ± 1.8 × 10 −30 and 6.6 ± 1.3 × 10 −24 cm 2 for σ RS and σ SERS respectively, we calculate an average cross-section enhancement factor (EF) of 0.8 ± 0.3 × 10 6 .

The absolute Raman scattering cross sections (σ RS ) for the 471, 217, and 153 cm −1 modes of sulfur were measured as 6.0 ± 1.2 × 10 −27 , 7.7 ± 1.6 × 10 −27 , and 1.2 ± 0.24 × 10 −26 cm 2 at 815, 799, and 794 nm, respectively, using a 785-nm pump laser. The corresponding values of σ RS at 1120, 1089, and 1081 nm were determined to be 1.5 ± 0.3 × 10 −27 , 1.2 ± 0.24 × 10 −27 , and 1.2 ± 0.24 × 10 −27 cm 2 using a 1064-nm laser. A temperature-controlled, small-cavity (2.125 mm diameter) blackbody source was used to calibrate the signal output of the Raman spectrometers for these measurements. Standoff Raman detection of a 6-mm-thick sulfur specimen located at 1500 m from the pump laser and the Raman spectrometer was made using a 1.4-W, CW, 785-nm pump laser.

The surface-enhanced Raman scattering (SERS) signal from an AgFON plasmonic substrate, recoated with benzenethiol, was observed to increase by about 100% upon heating for 3.5 min at 100 °C and 1.5 min at 125 °C. The signal intensity was found to increase further by about 80% upon a 10 s exposure to a high-intensity (3.2 kW/cm2) 785 nm CW laser, corresponding to 40 mW in a 40 ± 5 μm diameter spot. The observed increase in the SERS signal may be understood by considering the presence of benzenethiol molecules in an intermediate or “precursor” state in addition to conventionally ordered molecules forming a self-assembled monolayer. The increase in the SERS signal arises from the conversion of the molecules in the precursor state to the chemisorbed state due to thermal and photothermal effects.

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