jp051942z_si_002.txt (12.09 kB)
Mid-infrared Extinction Spectra and Optical Constants of Supercooled Water Droplets
datasetposted on 2005-08-18, 00:00 authored by Robert Wagner, Stefan Benz, Ottmar Möhler, Harald Saathoff, Martin Schnaiter, Ulrich Schurath
Complex refractive indices of supercooled liquid water have been retrieved at 269, 258, 252, and 238 K in the 4500−1100 cm-1 wavenumber regime from series of infrared extinction spectra of micron-sized water droplets. The spectra collection was recorded during expansion experiments in the large coolable aerosol chamber AIDA of Forschungszentrum Karlsruhe. A Mie inversion technique was applied to derive the low-temperature refractive index data sets by iteratively adjusting the room-temperature optical constants of liquid water until obtaining the best agreement between measured and calculated infrared spectra of the supercooled water droplets. The new optical constants, revealing significant temperature-induced spectral variations in comparison with the room-temperature refractive indices, proved to be in good agreement with data sets obtained in a recent study. A detailed analysis was performed to elaborate potential inaccuracies in the retrieval results when deriving optical constants from particle extinction spectra using an iterative procedure.
Mie inversion techniqueOptical Constantsconstantsupercooled water dropletsiterative procedureextinction spectraindex data setsspectra collectionSupercooled Water Droplets ComplexForschungszentrum Karlsruheexpansion experiments238 Kparticle extinction spectradata setsretrieval resultsindiceswavenumber regimecoolable aerosol chamber AIDA