General Introduction To Raman Spectroscopy

Raman spectroscopy directly probes a molecule's vibrational and rotational states via scattering from a molecule of merely one photon in a million. Unlike infrared spectroscopy, no sample preparation is required, nor is there interference due to water content in the sample. Samples can be analyzed against a library in the field using non-destructive, point-and-click instruments. For this reason, Raman spectroscopy has become a popular technique for identification and analysis in diverse fields like process and pharmaceuticals, explosives detection, semiconductor processing quality control, and biotechnology.

This introduction offers a valuable look at the capabilities and applications of Raman spectroscopy. The note introduces Coherent anti-Stokes Raman Scattering (CARS). This nonlinear four-wave mixing process enhances weak Raman signals, which is particularly useful in microscopy for chemically specific, label-free imaging at the sub-micron scale. CARS has been applied in cell biology, tissue imaging, and clinical applications, providing valuable insights into lipid metabolism, organelle transport, and drug diffusion. Surface-Enhanced Raman Scattering (SERS) is explained, highlighting its ability to amplify weak Raman signals using nanoscale roughened metal surfaces. SERS finds applications in analytical chemistry, drug discovery, forensic testing, detection of trace agents, and point-of-care medical diagnostics.

Stimulated Raman Scattering (SRS) microscopy is an alternative to CARS, offering background-free chemical imaging with improved contrast, particularly beneficial in biomedical imaging where water is a significant source of nonresonant background. Also detailed is UV Raman Spectroscopy, emphasizing the advantages of measuring Raman spectra in the ultraviolet (UV) wavelength range. This approach can substantially alleviate limitations related to small Raman scattering cross-sections and intrinsic noise sources like sample autofluorescence.

Please read the complete application note for a comprehensive overview of various Raman spectroscopy techniques and their applications along with recommendations for using advanced optical filters to enhance the performance of Raman spectroscopy systems.