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Abstract
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 60× 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 × 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 × 0.61 m × 0.61 m box.
Copyright 2015 American Association for Aerosol Research
ACKNOWLEDGMENTS
We thank William Herzog, Bradford Perkins, Steven Christesen (ECBC), and David Sickenberger (ECBC) for several discussions regarding this work. We thank Richard Kreis (ECBC) for the fabrication of the flow cell. We thank Brian Saar and Jay Eversole (NRL) for support of the virtual impactor work. Opinions, interpretation, and recommendations are those of the authors, and do not necessarily represent the view of the U.S. Government.
Funding
This work was sponsored by the Defense Threat Reduction Agency through the Edgewood Chemical and Biological Center under the Air Force Contract FA8721-05-C-0002.