Raman spectroscopy has been shown to be a viable method for explosives detection. Currently most forensic Raman systems are either large, powerful instruments for laboratory experiments or handheld instruments for in situ point detection. We have chosen to examine the performance of certain benchtop Raman probe systems with the goal of developing an inexpensive, portable system that could be used to operate in a field forensics laboratory to examine explosives-related residues or samples. To this end, a rugged, low distortion line imaging dispersive Raman spectrograph was configured to work at 830 nm laser excitation and was used to determine whether the composition of thin films of plastic explosives or small (e.g., ≤10？μm) particles of RDX or other explosives or oxidizers can be detected, identified, and quantified in the field. With 300？mW excitation energy, concentrations of RDX and PETN can be detected and reconstructed in the case of thin Semtex smears, but further work is needed to push detection limits of areal dosages to the ~1？μg/cm2 level. We describe the performance of several probe/spectrograph combinations and show preliminary data for particle detection, calibration and detection linearity for mixed compounds, and so forth. 1. Introduction There is an ever increasing need for inexpensive and reliable detection of trace chemicals on surfaces for security and military applications [1]. In the homeland security and military arenas, chemicals such as explosives, and chemical and biological warfare agents all continue to be potential threats. In the last decade, Raman spectroscopy, particularly in the visible and near-infrared (NIR) wavelengths, has emerged as a method to detect and identify materials in a rapid and inexpensive manner [2]. One compelling motivation for the use of Raman techniques is that the spectra are more straightforward to analyze than infrared spectra, due in part to narrower intrinsic linewidths. Often the analyte Raman spectra can be simply and quickly interpreted in terms of peak height and/or peak area comparisons with an appropriate database [2]. Component concentrations of plastic explosives, for example, appear to be treatable as simple linear superpositions of spectra, and quantifications can sometimes be done to about the 1% level of contamination with bulk samples [3]. As a consequence, identifying the provenance of materials, especially explosives, becomes more straightforward. Raman spectroscopy has transitioned from the research laboratory to a field analytical technique since it can rapidly detect and
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