Infrared Optical Constants for Carvone from the Mie Inversion of Aerosol Extinction Spectra

Abstract

Frequency-dependent, complex refractive indices for carvone in the mid-infrared from 750 to 5000 cm-1 have been inverted from the Fourier transform extinction spectra of laboratory-generated aerosols recorded at room temperature. The refractive indices obtained in this analysis are in good qualitative agreement with the results of a previous thin-film study of carvone. However, a full quantitative assessment of this agreement cannot be made as tabulated data for the previous study are no longer available. The refractive indices, or optical constants, reported here add to the small number of frequency-dependent refractive index data sets for other organic compounds that are available in the literature. Such data can be used to elucidate the optical properties of a substance, which are of critical importance in the interpretation of remote sensing data and in the evaluation of how atmospheric particulate matter consisting of organic compounds may affect climate change.

Infrared complex refractive indices for nopinone

“…Figure 3 shows a comparison of the nopinone k spectra to those reported for carvone [ Dohm et al , 2004]. Carvone is a keto‐monoterpene that is synthesized in plants and is the principal component in spearmint and caraway oils [ Whittaker , 1972].…”

“…Another gauge of precision is given by the average value of k which was found to be 0.341 ± 0.004. The uncertainty in this parameter is consistent with that of k as expected, given that it is equal to the maximum value of k throughout the spectrum and in theory is independent of the size distribution of the aerosol [Dohm et al, 2004].…”

“…[7] Complex refractive indices were inverted from the scattering extinction spectra of nopinone aerosols with an iterative procedure that is based on the method of Clapp et al [1995], with several modifications that have been detailed by Dohm et al [2004]. Briefly, the procedure is initiated by obtaining an estimate of the frequency dependence in k from a thin-film extinction spectrum, E, through k = E/4pLñ = kk 0 whereñ is the frequency in wavenumber (cm À1 ), k 0 is an imaginary component template whose maximum value is set to unity, and k is a parameter that principally accounts for uncertainty in the film thickness, L. This operation is done only once for computational convenience at the outset of the inversion; as indicated below, final k values are obtained strictly from aerosol extinction spectra.…”

Frequency Dependent Complex Refractive Indices of Supercooled Liquid Water and Ice Determined from Aerosol Extinction Spectra

“…3,11,12 The general algorithm used in the present study is given below In the above equations: K j,i V is the aerosol extinction cross section at the frequency ν i , normalized to the volume of a sphere with radius r j ; Q ext and Q scat are the extinction and scattering efficiency coefficients, respectively; n*(ν) ) n(ν) + ik(ν) is the complex refractive index; r is the particle radius; and ν is the frequency. The vector I is the (observed) extinction spectrum and 1 is the identity matrix.…”

Infrared Optical Constants of Organic Aerosols: Organic Acids and Model Humic-Like Substances (HULIS)

“…Wavelength dependent complex refractive indices were extracted from the experimentally measured extinction spectra using a Mie inversion procedure based on the Kramers-Krönig relations (Dohm et al 2004). The online supplemental information (SI) contains the details of the procedure and method validation that is supported with Figures S3-S9 and Tables S3 and S4.…”