News

17.12.2020

New ULF module to obtain Raman Stokes spectra

The CCiTUBs have just acquired an ULF (Ultra Low Frequency) module attached to the LabRam HR spectrometer that allows access to ultra-low Raman frequency regions between 5 and 100 cm^-1. Thanks to this extension, the Raman Unit of the CCiTUB can now offer "Raman Terahertz" (or THz-Raman) measurements, facilitating the study of a whole series of very low energy modes such as:

shear modes
rotational modes
acoustic modes
breathing modes
lattice modes
folding modes
heavy atom vibrations

The ULF module allows obtaining Raman Anti-Stokes spectra as well as Raman Stokes spectra simultaneously. In recent years, THz-Raman spectroscopy has become a fundamental method for the characterization and study of 2D layers (2-dimensional materials) such as MoS₂, grafè, MoTe₂, NbSe₂, and other transition metal dichalcogenide (TMD) monolayers. Access to ultra-low Raman frequencies also allows to:

► Detect the LAMs (Longitudinal acoustic Modes) in polymers and measure the modulus as well as the size of the lamellae
► Identify with great sensitivity very similar polymorphic phases in organic semiconductors or active pharmaceutical ingredients
► Obtain high resolution Stokes / anti-Stokes rotational spectra in gases
► Detect Shear modes in monolayers so determine the number of layers in graphene or other 2D materials.
► Analyze with great precision the conformational changes in organic crystals
► Perform studies of amorphous materials (boson peak, vibrational density of states (VDOS))
► Analyze networks in superconductors and superlattices
► Measure the breathing modes in nanotubes to determine diameters in nanotubes.

Samples of Raman Sokes spectra obtained in the CCiTUB with the ULF module: