Exploring Electronic Resonance Enhancement in 3-color Two-Beam Coherent Raman Scattering*

We report a new application and extension of our formerly developed and characterized instrumentation and spectral processing methods of two-beam 3-color broadband coherent Raman methodology [1]. The procedure was applied for molecular vibrational measurements over the low-frequency spectral domain. It was recognized that the method could be used to measure high-quality phonon spectra of crystals, but the effects of electronic enhancement have not been investigated. We now present new low-frequency vibrational spectra of, e.g., beta-carotene measured under electronic resonance conditions. We developed the necessary signal-processing method for the observed spectra because altered lineshapes and polarization were detected. 

[1] L. Ujj, Contribution to the development of low frequency terahertz coherent Raman micro-spectroscopy and microscopy, Spectrochim. Acta - Part A Mol. Biomol.Spectrosc. (2018), https://doi.org/10.1016/j.saa.2018.03.033.