Low-energy Raman spectra without background

What is it about?

In this work, we acquire low-energy Raman spectra via coherent Raman scattering techniques without any spectral background. Neither fluorescence nor non-resonant background is present. This is achieved by utilizing a combination of several progressive ideas developed in the fields of 2D electronic spectroscopy and coherent anti-Stokes Raman scattering (CARS). In this work, by measuring signals via both CARS and coherent Stokes Raman scattering (CSRS) methods, we show that it is possible to disentangle those contributions to the Raman signals that come from the vibrational dynamics on the excited electronic state from those that originate from the ground electronic state.

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Photo by anja. on Unsplash

Photo by anja. on Unsplash

Why is it important?

Understanding the nature of low-energy (<200 cm−1) vibrational modes is of high significance in several disciplines and can allow insights into the systems under investigation. In biological sciences, for example, low-frequency vibrations may be associated with large-scale nuclear motions in proteins, which can be associated with proteins’ ability to tune their reactivity or enhance energy transfer in photosynthetic light-harvesting. In condensed matter physics, low-frequency vibrations can, for example, characterize details of polycrystalline structures, determine the size of nanomaterials (e.g., 1D single-wall carbon nanotubes, 2D materials), and may assist with identification of a low-temperature noncentrosymmetric phase of matter, such as those that host exotic type-II Weyl fermions.

Perspectives