Raman Microspectroscopy
Definition
A vibrational spectroscopy technique using a focused laser beam to excite molecular vibrations in an ink sample. Non-destructive. Primary method for toner identification (carbon black D/G bands; polymer fingerprint) and inkjet dye / pigment characterisation.
- Primary forensic use
- Toner identification (carbon black D/G bands and polymer fingerprint) and inkjet dye/pigment characterization
- Key advantage
- Non-destructive analysis, preserves the sample for further testing
- Analysis scale
- Micrometre-scale resolution, enabling examination of individual paint layers
Common questions
What does Raman microspectroscopy actually do in forensics?+
It uses a focused laser beam to excite molecular vibrations in a tiny spot of material, then measures the light scattered back. The technique is non-destructive, so the sample survives the analysis. It works for ink toners, inkjet dyes, pigments, and paint extenders.
Why use this instead of just looking at ink or paint under a microscope?+
A regular microscope shows you color and shape, but not the chemical structure. Raman tells you what the material actually is. For toner, it identifies the carbon black fingerprint and polymer composition. For paint, it pinpoints pigments and extenders in cross-sections without destroying the sample.
How small is the area Raman can analyze?+
It works on a micrometre-scale spot, meaning it can examine tiny regions like a single paint layer in a cross-section. This precision makes it ideal for complex samples where different materials are layered together.
Related terms
- ASTM E2285 / E2286
- The two ASTM International standards governing forensic ink examination: E2285 covers TLC-based ink alteration examination; E2286 covers HPLC-based ink comparison. Both are...
- ASTM E2937
- ASTM International standard guide for identification of paint binders by pyrolysis-GC-MS; specifies pyrolysis conditions, GC column, oven program, and diagnostic ion reporting.
- ATR (Attenuated Total Reflectance)
- An FTIR sampling mode in which the sample is pressed against a diamond or ZnSe crystal and the evanescent wave probes the...
- Backscattered Electron (BSE) Imaging
- An SEM imaging mode sensitive to atomic number and crystallographic texture; can reveal grain-boundary elongation patterns in the sub-surface cold-worked zone after...
- Ballpoint Ink
- An oil-based, high-viscosity ink using a resin binder (alkyd or polyamide) in a high-boiling solvent (phenoxyethanol or benzyl alcohol), with triphenylmethane dyes...
- ENFSI EPG Protocol
- European Network of Forensic Science Institutes Expert Working Group on Paint protocol; the European standard for paint comparison examination sequence and reporting.
- FTIR Microspectroscopy
- Fourier-transform infrared spectroscopy collected from a microscope-focused spot of 10-20 µm diameter; the primary technique for paint binder characterisation.
- HPLC-DAD
- High-performance liquid chromatography with diode-array detection. Separates ink dyes on a C18 column and records UV-visible spectra at each elution point, providing...
- Iron-Gall Ink
- A historical ink formulation of ferrous sulphate, tannic acid (from oak galls), and gum arabic. The ferrous-tannate complex oxidises to brown ferric-tannate...
- IRUG Database
- Infrared and Raman Users Group spectral database; covers historic pigments, artists' materials, and museum-object coatings. Primary reference for art-investigation paint analysis.
- Likelihood Ratio Reporting
- A Bayesian framework for reporting paint-comparison conclusions, expressing the probability of the observed data given the hypothesis of common source versus the...
- Microtome Cross-Section
- A thin section of a paint chip cut perpendicular to the layer planes, allowing each layer to be examined separately by microscopy...
Explained in these topics
- Ink Chemistry: TLC, HPLC, Raman and the Video Spectral Comparator WorkflowA vibrational spectroscopy technique using a focused laser beam to excite molecular vibrations in an ink sample. Non-destructive. Primary method for toner iden...
- Paint Layer Examination: Cross-Section, FTIR and Py-GC-MSLaser-excited inelastic light scattering measured from a micrometre-scale spot; the primary technique for pigment and extender identification in paint cross-se...