Raman Spectroscopy for Homeland Security Applications

Abstract

Raman spectroscopy is an analytical technique with vast applications in the homeland security and defense arenas. The Raman effect is defined by the inelastic interaction of the incident laser with the analyte molecule's vibrational modes, which can be exploited to detect and identify chemicals in various environments and for the detection of hazards in the field, at checkpoints, or in a forensic laboratory with no contact with the substance. A major source of error that overwhelms the Raman signal is fluorescence caused by the background and the sample matrix. Novel methods are being developed to enhance the Raman signal's sensitivity and to reduce the effects of fluorescence by altering how the hazard material interacts with its environment and the incident laser. Basic Raman techniques applicable to homeland security applications include conventional (off-resonance) Raman spectroscopy, surface-enhanced Raman spectroscopy (SERS), resonance Raman spectroscopy, and spatially or temporally offset Raman spectroscopy (SORS and TORS). Additional emerging Raman techniques, including remote Raman detection, Raman imaging, and Heterodyne imaging, are being developed to further enhance the Raman signal, mitigate fluorescence effects, and monitor hazards at a distance for use in homeland security and defense applications.

Photonics for Forensic Applications

“…Portable Raman spectrometers have largely been used in forensics in the last years to detect narcotics, explosives, powders, chemical weapons, industrial chemicals 13,14 and for homeland security applications at larger extent 15 .…”

Detection of Nitro-aromatic Compound in Soil and Sand using Time Gated Raman Spectroscopy

“…Raman technique is a non-invasive instantaneous technique and it provides a 'finger print of the molecule' without any need of tunable laser [5][6] . Because of its ability to provide unique set of vibrational frequencies to identify molecular species, Raman spectroscopy has become an important tool for home land defence applications 7 .…”

Experimental examination of ultraviolet Raman cross sections of chemical warfare agent simulants

“…A non-contact method using a standoff/proximity measuring system is generally desirable in terms of security and efficiency [1]. Raman spectroscopy is expected to provide adequate classification for a fielded system [2] but is due to the low level of Raman scattering limited to relatively short measuring ranges, possibly up to a few meters [3].…”