Standoff Detection System Using Raman Spectroscopy in the Deep-Ultraviolet Wavelength Region for the Detection of Hazardous Gas

Abstract

This study developed a standoff detection system for Raman spectra in the deep-ultraviolet region to facilitate remote detection of various hazardous materials. Although Raman spectroscopy can distinguish various materials, the measurement of Raman spectra through standoff detection is challenging because of the low scattering cross-section of Raman scattering. The resonance Raman scattering effect in the deep-ultraviolet wavelength region is promising in terms of enhancing the spectral intensity of Raman scattering. A catoptric light receiver system was developed to effectively collect deep-ultraviolet light via a change in the distance from the primary to secondary mirror of the telescope. The experimental results for the standoff detection indicate that the system enables the measurement of the Raman spectrum of SO2 gas, which was locally present 20 m from the system with a wavelength resolution of 0.15 nm. The gas used in this remote measurement has a relatively simple molecular structure among chemical, biological, radiological, nuclear, and explosive gases. However, the high wavelength resolution of Raman spectroscopy will enable measurement of substances with complex molecular structures, such as bacteria and explosives, without losing the detailed structure of their spectra.