“…Although the Raman spectra of SO 2 were measured using the standoff detection scheme, the shape of the Raman spectrum was different to that reported in in a previous study. 18 The photodissociation of SO 2 may be a reason for the changed shape in the Raman spectrum. 19 The short-range measurement was performed by placing the laser and spectrometer close to the gas cell to investigate the change in the shape of the Raman spectrum of SO 2 in the standoff detection scheme.…”
Section: Discussionmentioning
confidence: 99%
“…Here, the long wavelength pass filter was not required to measure the spectrum in the experiment because the Raman spectrum could be clearly observed. The laser wavelength was set at 217 nm, where the resonance Raman effect for SO 2 molecule was confirmed, 18 and the multiple peaks observed near 1200 cm −1 and above 3000 cm −1 were the Raman spectra of SO 2 . To the best of the authors’ knowledge, this is the first recorded observation of the Raman spectra of toxic gases in the DUV wavelength range at a distance greater than 10 m from the light receiver system.Figure 6.Raman spectra when the gas cell, which was filled with a mixture of SO 2 and nitrogen gas adjusted to a concentration of 1000 ppm, was placed at 20 m from the light receiver system.…”
Section: Methodsmentioning
confidence: 99%
“…The reason why the laser pulse with a wavelength of 217 nm is that the Raman spectral intensity derived from SO 2 is enhanced by the resonance Raman effect when a laser pulse with a wavelength of 217 nm is used. 18 Further, the numerical aperture of the laser pulse and the beam diameter at the output end were evaluated based on the distance dependence of the beam diameter. The beam divergence at the wavelength of 217 nm was evaluated to be 3 mrad.…”
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 it measure substances with complex molecular structures, such as bacteria and explosives, without losing the detailed structure of their spectra.
“…Although the Raman spectra of SO 2 were measured using the standoff detection scheme, the shape of the Raman spectrum was different to that reported in in a previous study. 18 The photodissociation of SO 2 may be a reason for the changed shape in the Raman spectrum. 19 The short-range measurement was performed by placing the laser and spectrometer close to the gas cell to investigate the change in the shape of the Raman spectrum of SO 2 in the standoff detection scheme.…”
Section: Discussionmentioning
confidence: 99%
“…Here, the long wavelength pass filter was not required to measure the spectrum in the experiment because the Raman spectrum could be clearly observed. The laser wavelength was set at 217 nm, where the resonance Raman effect for SO 2 molecule was confirmed, 18 and the multiple peaks observed near 1200 cm −1 and above 3000 cm −1 were the Raman spectra of SO 2 . To the best of the authors’ knowledge, this is the first recorded observation of the Raman spectra of toxic gases in the DUV wavelength range at a distance greater than 10 m from the light receiver system.Figure 6.Raman spectra when the gas cell, which was filled with a mixture of SO 2 and nitrogen gas adjusted to a concentration of 1000 ppm, was placed at 20 m from the light receiver system.…”
Section: Methodsmentioning
confidence: 99%
“…The reason why the laser pulse with a wavelength of 217 nm is that the Raman spectral intensity derived from SO 2 is enhanced by the resonance Raman effect when a laser pulse with a wavelength of 217 nm is used. 18 Further, the numerical aperture of the laser pulse and the beam diameter at the output end were evaluated based on the distance dependence of the beam diameter. The beam divergence at the wavelength of 217 nm was evaluated to be 3 mrad.…”
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 it measure substances with complex molecular structures, such as bacteria and explosives, without losing the detailed structure of their spectra.
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