Recently, the diverse scope of ultra-low frequency Raman studies has greatly grown because interlayer and skeletal vibrations are located at <100 cm-1 correlated to specific interactions of functional materials, such as graphene, WS2, and perovskites. However, quantitative analyses using absolute Raman cross-sections (σR) have less studied than qualitative analyses using normalized Raman spectra.
σR is the effective area proportional to the possibility of Raman scattering by an incident excitation. This σR can be determined by Equation 1. F is the integrated area under the photon flux for Raman mode. Pp is the pump power incident upon the sample. N is the atomic concentration of sulfur and L is the effective thickness that contributes to scattering. hvp is the photon pump energy. ƞc is the optical collection efficiency of Raman spectrometer.
We have developed a home-built ultra-low frequency Raman spectrometer and measured σR of sulfur at <200 cm-1. (Figure 1) In this talk, we will present our on- and off-resonant absolute σR values of sulfur. We expect these σR of sulfur can be the relative references for quantitative ultra-low frequency Raman studies of materials.