Highlighting The Greatest Hits in Molecular Spectroscopy Workbench Column

Molecular spectroscopy is an analytical technique used to study the interaction of molecules with electromagnetic radiation (1). It provides valuable insights into molecular structure, composition, and dynamics by measuring how molecules absorb, emit, or scatter light across different wavelengths (1). This technique is widely applied in chemistry, physics, biology, and materials science. Several of the most commonly used molecular spectroscopy techniques include infrared (IR) spectroscopy and Raman spectroscopy.

In our “Molecular Spectroscopy Workbench” column, columnist Fran Adar, who is a Principal Raman Applications Scientist for Horiba Scientific and a member of Spectroscopy magazine’s editorial advisory board, explores the application of molecular spectroscopy and explains the fundamental principles underlying molecular spectroscopy techniques (1).

Below is a compilation of some of the most popular “Molecular Spectroscopy Workbench” columns, according to our readers and subscribers. Happy reading!

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A Proposal for the Origin of the Near-Ubiquitous Fluorescence in Raman Spectra

Fluorescence often interferes with Raman spectroscopy, making it difficult to extract meaningful spectral information (2). Both Raman and fluorescence emissions appear on the long-wavelength side of the excitation laser but distinguishing them is key (2). Raman signals exhibit sharp lines that shift with the laser wavelength, while fluorescence appears as a broad, intense background that remains fixed in nanometers (2). In this “Molecular Spectroscopy Workbench” column, columnist Fran Adar explores the origin of fluorescence in Raman spectra, supported by PAH measurements, to help analysts minimize interference and optimize experimental conditions.

Raman Microscopy for Characterizing Defects in SiC

Silicon carbide (SiC) is a wide bandgap semiconductor ideal for high-power circuits due to its ability to carry high currents without overheating (3). Its cubic phase shares a tetrahedral structure with silicon, diamond, and germanium, but SiC also forms multiple polymorphs due to variations in stacking order. These structural differences impact crystal growth, potentially leading to defects that affect device performance (3). In this “Molecular Spectroscopy Workbench” column, it is explained why Raman microscopy is essential for analyzing SiC because it can distinguish polymorphs, detect contaminants, and reveal doping levels above 2×10¹⁶, making it a valuable tool for semiconductor material qualification.

Evaluating a Multilayer Polymer Film by Raman Microscopy

Multilayer polymer films combine different polymers for specific functions, requiring precise analysis for troubleshooting or reverse engineering (4). Confocal Raman microscopy has long been considered a non-destructive method for analyzing these films, offering submicron optical resolution beneath surfaces (4). However, focusing errors occur because of material refraction, especially at greater depths and higher numerical apertures (4). This article compares a depth profile with a cross-sectional Raman map to assess the accuracy of depth profiling, helping refine analytical approaches for multilayer film characterization.

Monitoring Chemical Changes by Raman Spectroscopy

Raman spectroscopy enables real-time monitoring of chemical reactions, including polymerization, by detecting strong signals from π electrons as carbon double bonds break (5). This makes it highly effective for tracking polymerization progress. However, demonstrating such reactions can be hazardous (5). This “Molecular Spectroscopy Workbench” column explores the chemical and spectral changes during the curing of a commercial epoxy, showcasing Raman spectroscopy’s capabilities in observing reaction dynamics safely and effectively.

Raman Spectra Used to Understand the Origins of Banding in Spherulites

Spherulite formation in polymers occurs during crystallization from the melt, where crystal lamellae grow radially from a nucleation site (6). When annealed on a planar surface and viewed under crossed polarizers, a Maltese cross with banding appears due to crystal orientation (6). Since polarized Raman spectra respond to crystal orientation, this “Molecular Spectroscopy Workbench” column explores the relationship between banding patterns and Raman polarization behavior. Results from poly(hydroxybutyrate-co-hydroxyhexanoate) (PHBHx) spherulites with varying compositions are presented to examine this correlation (6).

References

1. Li, J.; Fernandez, R.; Gutierrez, B.; et al. Advancing Molecular Spectroscopy Efficiency with Extensive Parallelism. Metrology 2024, 4 (4), 736–764. DOI: 10.3390/metrology4040043
2. Adar, F. A Proposal for the Origin of the Near-Ubiquitous Fluorescence in Raman Spectra. Spectroscopy 2025, 40 (2), 8–12. DOI: 10.56530/spectroscopy.ta7090c5
3. Adar, F. Raman Microscopy for Characterizing Defects in SiC. Spectroscopy 2024, 39 (8), 8–13. DOI: 10.56530/spectroscopy.sy4978n2
4. Adar, F. Evaluating a Multilayer Polymer Film by Raman Microscopy. Spectroscopy 2024, 39 (5), 8–13. DOI: 10.56530/spectroscopy.kx2574a8
5. Adar, F. Monitoring Chemical Changes by Raman Spectroscopy. Spectroscopy 2024, 39 (2), 8–10. DOI: 10.56530/spectroscopy.ia6269u7
6. Adar, F. Raman Spectra Used to Understand the Origins of Banding in Spherulites. Spectroscopy 2023, 38 (11), 8–13. DOI: 10.56530/spectroscopy.wu2080k9