Detection of hazardous chemical using dual-wavelength Raman spectroscopy in the ultraviolet region.

ABSTRACT

This study proposes a stand-off Raman spectroscopy system using dual-wavelength in the ultraviolet (UV) region to detect hazardous chemicals. The Raman spectrum generated by the UV excitation source avoids solar background noise during daytime for chemical detection as the spectrum is in the solar blind range. Wavelengths of 213 and 266 nm by 5th and 4th harmonics are generated from NdYAG laser. However, Raman spectra of chemicals exhibit different signal-to-noise ratios for both the excitation wavelengths; therefore, to detect such chemicals, Raman spectra by two sources are required. Raman spectra were acquired using a dual-wavelength laser and spectrometer with a single grating and detector at the wavelengths of 213 and 266 nm simultaneously. The Raman spectra of sulfuric acid, 2-chloroethyl ethyl sulfide, and dimethyl methylphosphonate were acquired and analyzed, thus highlighting the application of dual-wavelength Raman spectroscopy. For efficient chemical detection in the field, we have ensured that the system developed in this study is robust.