Systematic spectral shifts in the mid-infrared spectroscopy of aerosols

Luke Maidment, Peter G. Schunemann, Rhea J. Clewes, Martin D. Bowditch, Christopher R. Howle, Derryck Telford Reid

Research output: Contribution to journalArticle

1 Citation (Scopus)
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Abstract

Infrared spectroscopy in the spectral fingerprint region from 6.5 to 20 µm has been applied for decades to identify vapor- and condensed-phase chemicals with high confidence. By employing a unique broadband laser operating from 7.2- to 11.5-µm we show that, in this region, wavelength-dependent Mie-scattering effects substantially modulate the underlying chemical absorption signature, undermining the ability of conventional infrared absorption spectroscopy to identify aerosolized liquids and solids. In the aerosol studied, Mie theory predicts that the positions of spectroscopic features will blue-shift by up to 200 nm, and this behavior is confirmed by experiment, illustrating the critical importance of considering Mie contributions to aerosol spectroscopy in the mid infrared. By examining the spectroscopy of light scattered from an aerosol of the chemical diethyl phthalate, we demonstrate excellent agreement with a Mie-scattering model informed by direct measurements of the particle-size-distribution and complex refractive index.

Original languageEnglish
Pages (from-to)18975-18981
Number of pages7
JournalOptics Express
Volume26
Issue number15
Early online date11 Jul 2018
DOIs
Publication statusPublished - 23 Jul 2018

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

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