Raman Spectroscopy
Definition
A non-destructive laser-based technique sensitive to molecular vibration modes in pigments; complements FTIR by characterising pigment molecular structure rather than bulk ink chemistry; used to identify pigment species and detect proprietary modifications in genuine banknote pigments.
- Excitation wavelengths common
- 785 nm and 1064 nm for document analysis, chosen to suppress background fluorescence from paper
- Non-destructive
- Leaves samples intact, critical for evidence preservation
- Field instruments
- TruNarc, Progeny ResQ, NanoRam enable portable analysis
- Applications
- Document inks, currency pigments, explosives, blood aging
Common questions
What is Raman spectroscopy and how does it work in forensics?+
Raman spectroscopy is a technique that shines a laser on a sample and measures how light scatters off molecules. The scattered light carries a molecular fingerprint that reveals what's actually present. It works without damaging the sample, making it ideal for documents, currency, and explosives analysis.
How is Raman spectroscopy different from other techniques like FTIR?+
While FTIR looks at how materials absorb infrared light, Raman measures the vibration modes of molecules directly through inelastic light scattering. This means Raman can identify specific pigments and their molecular structure, not just bulk ink chemistry. It's especially useful when you need to spot proprietary modifications in materials like banknotes.
Can Raman spectroscopy detect explosives in the field?+
Yes. Handheld Raman devices like TruNarc and NanoRam can identify bulk explosives through barriers in under 30 seconds, providing rapid field screening without opening packages or handling hazardous materials.
Related terms
- 3-D Surface Profilometry
- A non-contact optical measurement technique used to quantify the topographic height (Z-height) of intaglio ink ridges; genuine MGNS intaglio measures 15-40 micrometres;...
- 365 Nm UV Lamp
- A long-wave ultraviolet lamp used to examine substrate fluorescence, security thread UV response, and UV-reactive features on banknotes; genuine cotton-linen substrate appears...
- Aginsky Method
- Solvent-extraction ink-age dating (Valery Aginsky, 1996). Compares fast and slow solvent extractions of phenoxyethanol to derive an aging parameter for ink under...
- ASTM E2789-11
- ASTM standard guide for forensic examination of inks (ink-age dating context). Pairs with ASTM E1422 for paper examination by FTIR.
- Attenuated Total Reflectance (ATR) FTIR
- An infrared spectroscopy configuration where the IR beam passes through an ATR crystal and generates an evanescent wave that samples a thin...
- 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...
- Bleached-Genuine Counterfeit
- A counterfeit produced by chemically removing the printed design from a genuine lower-denomination note and reprinting it as a higher denomination; passes...
- Brunelle R-Ratio Method
- Dye-degradation method (Richard Brunelle and Kenneth Pro, 1972, later refined). Tracks the ratio of extracted and unextracted dye over time to estimate...
- Counterfeit Currency Database (CCD)
- The US Secret Service's classification registry of counterfeit production signatures, assigning class codes to each distinct printing-process and denomination combination detected in...
- CVPC (Currency Verification Processing Centre)
- An RBI-designated facility in India where banks submit suspect notes for initial authentication and classification before forensic referral.
- Diphenylamine (DPA) Test
- A broad-spectrum presumptive colour test for nitrate and nitrite compounds, producing a blue-green coloration. Reactive with multiple oxidising agents, so environmental context...
- Dye-Based Ink
- Soluble colourant dissolved in solvent. Modern fountain-pen and dye-based ballpoint inks belong here. TLC separates the dye mixture into resolvable spots.
Explained in these topics
- Counterfeit Currency Detection: Instruments and Field MethodsA non-destructive laser-based technique sensitive to molecular vibration modes in pigments; complements FTIR by characterising pigment molecular structure rath...
- Field Explosives Detection: IMS, ETD, Canines and RamanA vibrational spectroscopy technique based on inelastic scattering of laser photons. Produces a molecular fingerprint spectrum; handheld instruments (TruNarc,...
- Inks, Papers and Age of DocumentsVibrational scattering technique, non-destructive, 785 nm or 1064 nm excitation common for inks to suppress paper fluorescence; identifies dyes, pigments and r...
- Spectroscopic Methods for Bloodstain AgeingTechnique that measures inelastic scattering of monochromatic light by molecules. The frequency shift of scattered photons is characteristic of molecular bond...