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Raman Detection of a Single Airborne Aerosol Particles of Isovanillin(3.09 MB)

May 24, 2017
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Journal Article
Author:
Roshan L. Aggarwal
…
Published in:
AIP Advances, vol. 7, no. 5
Topic:
chemical technologies
R&D area:
R&D group:

Summary

Raman spectroscopy of trapped single aerosol particles has been reported previously. However, detection of single aerosol particles via Raman spectroscopy in a flowing system has not been yet reported. In this paper, we describe the first detection of single 3 um flowing airborne aerosol particles flowing through a Raman system, which is a simplified version of the previously reported system with a 532-nm, 10W cw double-pass laser, 532-nm isolator, and double-sided collection optics. The current system has single-pass laser, no 532-nm isolator, and single-sided collection optics. Previous Raman detection of single aerosol particles has been made using trapped particles.
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Summary

Raman spectroscopy of trapped single aerosol particles has been reported previously. However, detection of single aerosol particles via Raman spectroscopy in a flowing system has not been yet reported. In this paper, we describe the first detection of single 3 um flowing airborne aerosol particles flowing through a Raman system...

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Raman Detection of a Single Airborne Aerosol Particles of Isovanillin

Raman spectra and cross sections of ammonia, chlorine, hydrogen sulfide, phosgene, and sulfur dioxide toxic gases in the fingerprint region 400-1400 cm-1

February 11, 2016
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Journal Article
Author:
Roshan L. Aggarwal
…
Published in:
AIP Advances, Vol. 6, No. 2, February 2016, 025310, doi: 10.1063/1.4942109.
Topic:
chemical technologies
R&D area:
R&D group:

Summary

Raman spectra of ammonia (NH3), chlorine (Cl2), hydrogen sulfide (H2S), phosgene (COCl2), and sulfur dioxide (SO2) toxic gases have been measured in the fingerprint region 400-1400 cm-1. A relatively compact (< 2'x2'x2'), sensitive, 532 nm 10 W CW Raman system with double-pass laser and double-sided collection was used for these measurements. Two Raman modes are observed at 934 and 967 cm-1 in NH3. Three Raman modes are observed in Cl2 at 554, 547, and 539 cm-1, which are due to the 35/35 35/37, and 37/37 Cl isotopes, respectively. Raman modes are observed at 870, 570, and 1151 cm-1 in H2S, COCl2, and SO2, respectively. Values of 3.68 ± 0.26x10-32 cm2/sr (3.68 ± 0.26x10-36 m2/sr), 1.37 ± 0.10x10-30 cm2/sr (1.37 ± 0.10x10-34 m2/sr), 3.25 ± 0.23x10-31 cm2/sr (3.25 ± 0.23x10-35 m2/sr), 1.63 ± 0.14x10-30 cm2/sr (1.63 ± 0.14x10-34 m2/sr), and 3.08 ± 0.22x10-30 cm2/sr (and 3.08 ± 0.22x10-34 m2/sr) were determined for the differential Raman cross section of the 967 cm-1 mode of NH3, sum of the 554, 547, and 539 cm-1 modes of Cl2, 870 cm-1 mode of H2S, 570 cm-1 mode of COCl2, and 1151 cm-1 mode of SO2, respectively, using the differential Raman cross section of 3.56 ± 0.14x10-31 cm2/sr (3.56 ± 0.14x10-35 m2/sr) for the 1285 cm-1 mode of CO2 as the reference.
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Summary

Raman spectra of ammonia (NH3), chlorine (Cl2), hydrogen sulfide (H2S), phosgene (COCl2), and sulfur dioxide (SO2) toxic gases have been measured in the fingerprint region 400-1400 cm-1. A relatively compact ( 2'x2'x2'), sensitive, 532 nm 10 W CW Raman system with double-pass laser and double-sided collection was used for these...

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Raman spectra and cross sections of ammonia, chlorine, hydrogen sulfide, phosgene, and sulfur dioxide toxic gases in the fingerprint region 400-1400 cm-1

Sensitive detection and identification of isovanillin aerosol particles at the pg/cm^3 mass concentration level using Raman spectroscopy

June 8, 2015
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Journal Article
Author:
Roshan L. Aggarwal
…
Published in:
Aerosol Sci. Technol., Vol. 49, No. 9, 2015, pp. 753-6.
Topic:
detection systems
R&D area:
R&D group:

Summary

A compact Raman spectroscopy system with high sensitivity to chemical aerosols has been developed. This system has been used to detect isovanillin aerosols with mass concentration of 12 pg/cm3 in a 15 s signal integration period with a signal-to-noise ratio of 32. We believe this represents the lowest chemical aerosol concentration and signal integration period product ever reported for a Raman spectroscopy system. The Raman system includes (i) a 10 W, 532-nm cw laser, (ii) an aerosol flow cell, (iii) a 60x aerosol concentrator, (iv) an f/1.8 Raman spectrometer with a spectral range of 400-1400 cm^-1 and a resolution of 4 cm^-1, and (v) a low-noise CCD camera (1340 x 400 pixels). The collection efficiency of the Raman system has been determined to be 2.8%. Except for the laser cooling subsystem, the Raman system fits in a 0.61 m x 0.61 m x 0.61 m box.
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Summary

A compact Raman spectroscopy system with high sensitivity to chemical aerosols has been developed. This system has been used to detect isovanillin aerosols with mass concentration of 12 pg/cm3 in a 15 s signal integration period with a signal-to-noise ratio of 32. We believe this represents the lowest chemical aerosol...

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Sensitive detection and identification of isovanillin aerosol particles at the pg/cm^3 mass concentration level using Raman spectroscopy

Chemical aerosol detection and identification using Raman scattering

August 1, 2014
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Journal Article
Author:
Roshan L. Aggarwal
…
Published in:
J. Raman Spectrosc., Vol. 45, No. 8, August 2014, pp. 677-9.
Topic:
detection systems
R&D area:
R&D group:

Summary

Early warning of the presence of chemical agent aerosols is an important component in the defense against such agents. A Raman spectrometer has been constructed for the purpose of detecting and identifying chemical aerosols. We report the detection and identification of a low-concentration chemical aerosol in atmospheric air using 532-nm continuous wave laser Raman scattering. We have demonstrated the Raman scattering detection and identification of an aerosol of isovanillin of mass concentration of 1.8 ng/cm^3 with a signal-to-noise ratio of about 19 in 30 s for the 116-cm^-1 mode with a Raman cross section of 3.3 x 10^-28 cm^2 using 8-W double-pass laser power.
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Summary

Early warning of the presence of chemical agent aerosols is an important component in the defense against such agents. A Raman spectrometer has been constructed for the purpose of detecting and identifying chemical aerosols. We report the detection and identification of a low-concentration chemical aerosol in atmospheric air using 532-nm...

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Chemical aerosol detection and identification using Raman scattering

Measurement of the surface-enhanced coherent anti-Stokes Raman scattering (SECARS) due to the 1574 cm^-1 surface-enhanced Raman scattering (SERS) mode of benzenethiol using low-power (<20 mW) CW diode lasers

February 1, 2013
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Journal Article
Author:
Roshan L. Aggarwal
…
Published in:
Appl. Spectrosc., Vol. 67, No. 2, February 2013, pp. 132-135.
Topic:
lasers
R&D area:
R&D group:

Summary

The surface-enhanced coherent anti-Stokes Raman scattering (SECARS) from a self-assembled monolayer (SAM) of benzenethiol on a silver-coated surface-enhanced Raman scattering (SERS) substrate has been measured for the 1574 cm^-1 SERS mode. A value of 9.6 +- 1.7 x 10^-14 W was determined for the resonant component of the SECARS signal using 17.8 mW of 784.9 nm pump laser power and 7.1 mW of 895.5 nm Stokes laser power; the pump and Stokes lasers were polarized parallel to each other but perpendicular to the grooves of the diffraction grating in the spectrometer. The measured value of resonant component of the SECARS signal is in agreement with the calculated value of 9.3 x 10^-14 W using the measured value of 8.7 +- 0.5 cm^-1 for the SERS linewidth Gamma (full width at half-maximum) and the value of 5.7 +- 1.4 x 10^-7 for the product of the Raman cross section rSERS and the surface concentration Ns of the benzenethiol SAM. The xxxx component of the resonant part of the third-order nonlinear optical susceptibility |3X (3)R/xxxx| for the 1574 cm^-1 SERS mode has been determined to be 4.3 +- 1.1 x 10^-5 cm g^-1 s^2. The SERS enhancement factor for the 1574 cm^-1 mode was determined to be 3.6 +- 0.9 x 10^7 using the value of 1.8 x 10^15 molecules/cm^2 for Ns.
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Summary

The surface-enhanced coherent anti-Stokes Raman scattering (SECARS) from a self-assembled monolayer (SAM) of benzenethiol on a silver-coated surface-enhanced Raman scattering (SERS) substrate has been measured for the 1574 cm^-1 SERS mode. A value of 9.6 +- 1.7 x 10^-14 W was determined for the resonant component of the SECARS signal...

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Measurement of the surface-enhanced coherent anti-Stokes Raman scattering (SECARS) due to the 1574 cm^-1 surface-enhanced Raman scattering (SERS) mode of benzenethiol using low-power (<20 mW) CW diode lasers

Measurement of the third-order nonlinear optical susceptibility chi^(3) for the 1002-cm^-1 mode of benzenethiol using coherent anti-Stokes Raman scattering with continuous-wave diode lasers

July 1, 2012
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Journal Article
Author:
Roshan L. Aggarwal
…
Published in:
J. Raman Spectrosc., Vol. 43, No. 7, July 2012, pp. 911-916.
Topic:
lasers
R&D area:
R&D group:

Summary

The components of the third-order nonlinear optical susceptibility x^(3) for the 1002-cm^?1 mode of neat benzenethiol have been measured using coherent anti-Stokes Raman scattering with continuous-wave diode pump and Stokes lasers at 785.0 and 852.0 nm, respectively. Values of 2.8±0.3 X 10^-12, 2.0±0.2 X 10^-12, and 0.8±0.1 X 10^-12 cmg^-1 s^2 were measured for the xxxx, xxyy, and xyyx components of |3x^(3)|, respectively. We have calculated these quantities using a microscopic model, reproducing the same qualitative trend. The Raman cross-section sigma RS for the 1002-cm^-1 mode of neat benzenethiol has been determined to be 3.1±0.6 X 10^-29 cm^2 per molecule. The polarization of the anti-Stokes Raman scattering was found to be parallel to that of the pump laser, which implies negligible depolarization. The Raman linewidth (full-width at half-maximum) Gamma was determined to be 2.4±0.3 cm^-1 using normal Stokes Raman scattering. The measured values of sigma RS and Gamma yield a value of 2.1±0.4 X 10^-12 cmg^-1 s^2 for the resonant component of 3x^(3). A value of 1.9±0.9 X 10^-12 cmg^-1 s^2 has been deduced for the nonresonant component of 3x^(3).
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Summary

The components of the third-order nonlinear optical susceptibility x^(3) for the 1002-cm^?1 mode of neat benzenethiol have been measured using coherent anti-Stokes Raman scattering with continuous-wave diode pump and Stokes lasers at 785.0 and 852.0 nm, respectively. Values of 2.8±0.3 X 10^-12, 2.0±0.2 X 10^-12, and 0.8±0.1 X 10^-12 cmg^-1...

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Measurement of the third-order nonlinear optical susceptibility chi^(3) for the 1002-cm^-1 mode of benzenethiol using coherent anti-Stokes Raman scattering with continuous-wave diode lasers

Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6-mm-thick sulfur specimen at 1500m

March 1, 2011
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Journal Article
Author:
Roshan L. Aggarwal
…
Published in:
J. Raman Spectr., Vol. 42, No. 3, March 2011, pp. 461-464.
Topic:
detection systems
R&D area:
R&D group:

Summary

The absolute Raman scattering cross sections (σRS) for the 471, 217, and 153 cm−1 modes of sulfur were measured as 6.0 ± 1.2 × 10−27, 7.7 ± 1.6 × 10−27, and 1.2 ± 0.24 × 10−26 cm2 at 815, 799, and 794 nm, respectively, using a 785-nm pump laser. The corresponding values of σRS at 1120, 1089, and 1081 nm were determined to be 1.5 ± 0.3 × 10−27, 1.2 ± 0.24 × 10−27, and 1.2 ± 0.24 × 10−27 cm2 using a 1064-nm laser. A temperature-controlled, small-cavity (2.125 mm diameter) blackbody source was used to calibrate the signal output of the Raman spectrometers for these measurements. Standoff Raman detection of a 6-mm-thick sulfur specimen located at 1500 m from the pump laser and the Raman spectrometer was made using a 1.4-W, CW, 785-nm pump laser.
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Summary

The absolute Raman scattering cross sections (σRS) for the 471, 217, and 153 cm−1 modes of sulfur were measured as 6.0 ± 1.2 × 10−27, 7.7 ± 1.6 × 10−27, and 1.2 ± 0.24 × 10−26 cm2 at 815, 799, and 794 nm, respectively, using a 785-nm pump laser. The...

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Measurement of the absolute Raman scattering cross sections of sulfur and the standoff Raman detection of a 6-mm-thick sulfur specimen at 1500m
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