Chemistry

Raman can be used to identify chemical species throughout reactions, or to monitor reaction rates by looking at the intensity of spectral features specific to reactants, catalysts and products. Raman signal is typically quite weak, but techniques like Resonance Raman exploit specific light absorption properties of molecules over a given wavelength range to provide significant Raman signal enhancement.

For organic species, Raman signal competes with fluorescence from the sample - a near-infrared laser or UV laser (with wavelength outside the absorption range of the molecule) can be used to greatly minimise or supress unwanted fluorescence contribution.

Coherent Anti-Stokes Raman (CARS) is a technique also used to determine non-invasively temperature and species concentration information in flames/combustion environments.

Further Reading

Bio-materials

Analytical spectroscopy techniques like Raman provide a powerful tool for the study of chemical and structural properties of biological, organic samples e.g. cells, tissues or viruses/pathogens. NIR photons allow deeper probing into these biological due to their greater penetration depth, and also provide higher diagnostics accuracy for Raman-based techniques by moving away from the unwanted autofluorescence background of these samples.

This can be used for non-invasive cancer and disease diagnostics with a high degree of Specificity, Sensitivity, Reproducibility and speed/throughput. It is also increasingly applied to real-time diagnostics in vivo, providing for example feedback to surgeon during intraoperative procedures to ensure full removal of cancerous tissues.

Further Reading

Process Control, QA/QC

Raman spectroscopy can be deployed in industrial environments to provide non-invasive, rapid feedback on efficiency of processes e.g. on-line monitoring of petrochemicals or manufactured/synthesized products quality e.g. tablets in the pharmaceutical industry (mapping of active components distribution), wafer quality control in the semiconductor industry (identification of defects/stress).

It provides for example highly specific information on the chemical make-up of a variety of samples in different environment. In the NIR Raman can be used to probe chemical species through opaque (and potentially fluorescent) materials using Surface Offset Raman Spectroscopy (SORS).

It can also be used to provide spatially-resolved feedback on defects, impurities or stress in wafers that can subsequently impact the performance of semiconductor device.

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