Dependent scattering and absorption by densely packed discrete spherical particles: Effects of complex refractive index

Abstract. Optical particle counters (OPC) are widely used to measure the aerosol particle number size distribution at atmospheric ambient conditions and over a large size range. Their measurement principle is based on the dependence of light scattering on particle size. However, this dependence is not monotonic at all sizes and light scattering also depends on the particle composition (i.e., the complex refractive index, CRI) and morphology. Therefore, the conversion of the measured scattered intensity to the desired particle size depends on the microphysical properties of the sampled aerosol population and might not be unique at all sizes. While these complexities have been addressed before, corrections are typically applied ad-hoc and are not standardised. This paper addresses this issue by providing a consistent and extended database of pre−computed correction factors for a wide range of complex refractive index values representing the composition variability of atmospheric aerosols. These correction factors are calculated for five different commercial OPCs (USHAS, PCASP, FSSP, GRIMM and its airborne version Sky− GRIMM, CDP) by assuming Mie theory for homogeneous spherical particles, and by varying the real part of the CRI between 1.33 and 1.75 in steps of 0.01 and the imaginary part between 0.0 and 0.4 in steps of 0.001. Correction factors for mineral dust are provided at the CRI of 1.53 – 0.003i and account for the asphericity of these particles. The datasets described in this paper are distributed at open-access repository: https://doi.org/10.25326/234 (license CC BY, Formenti et al., 2021) maintained by the French national center for Atmospheric data and services AERIS to data users/geophysicists who number size distribution measurements from OPC for their research on atmospheric aerosols. Application and caveats of the CRI-corrections factors are presented and discussed. The dataset presented in this paper is not only useful for correcting the size distribution from an OPC when the particle refractive index is known, but even when only assumptions can be made. Furthermore, this dataset can be useful in calculating uncertainties or sensitivities of aerosol volume/mass/extinction from OPCs given no or limited knowledge of refractive index.

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S-approximation for spherical particles with a complex refractive index

Optics and Spectroscopy ◽

10.1134/1.1454032 ◽

2002 ◽

Vol 92 (2) ◽

pp. 221-226 ◽

Cited By ~ 1

Author(s):

A. Ya. Perel’man ◽

V. Voshchinnikov

Keyword(s):

Refractive Index ◽

Complex Refractive Index ◽

Spherical Particles

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Broadband spectroscopy of astrophysical ice analogues

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935619 ◽

2019 ◽

Vol 629 ◽

pp. A112 ◽

Cited By ~ 8

Author(s):

B. M. Giuliano ◽

A. A. Gavdush ◽

B. Müller ◽

K. I. Zaytsev ◽

T. Grassi ◽

...

Keyword(s):

Refractive Index ◽

Optical Properties ◽

Time Domain ◽

Complex Refractive Index ◽

Far Infrared ◽

Infrared Region ◽

Thz Radiation ◽

The Real ◽

Thz Range ◽

The Time Domain

Context. Reliable, directly measured optical properties of astrophysical ice analogues in the infrared and terahertz (THz) range are missing from the literature. These parameters are of great importance to model the dust continuum radiative transfer in dense and cold regions, where thick ice mantles are present, and are necessary for the interpretation of future observations planned in the far-infrared region. Aims. Coherent THz radiation allows for direct measurement of the complex dielectric function (refractive index) of astrophysically relevant ice species in the THz range. Methods. We recorded the time-domain waveforms and the frequency-domain spectra of reference samples of CO ice, deposited at a temperature of 28.5 K and annealed to 33 K at different thicknesses. We developed a new algorithm to reconstruct the real and imaginary parts of the refractive index from the time-domain THz data. Results. The complex refractive index in the wavelength range 1 mm–150 μm (0.3–2.0 THz) was determined for the studied ice samples, and this index was compared with available data found in the literature. Conclusions. The developed algorithm of reconstructing the real and imaginary parts of the refractive index from the time-domain THz data enables us, for the first time, to determine the optical properties of astrophysical ice analogues without using the Kramers–Kronig relations. The obtained data provide a benchmark to interpret the observational data from current ground-based facilities as well as future space telescope missions, and we used these data to estimate the opacities of the dust grains in presence of CO ice mantles.

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The complex refractive index of dusty plasma

Optik ◽

10.1016/j.ijleo.2019.163078 ◽

2019 ◽

Vol 194 ◽

pp. 163078

Author(s):

Xu Meng ◽

Chen Yun-yun ◽

Cui Fen-ping

Keyword(s):

Refractive Index ◽

Dusty Plasma ◽

Complex Refractive Index

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Optical Characterization of Ultra-Thin Films of Azo-Dye-Doped Polymers Using Ellipsometry and Surface Plasmon Resonance Spectroscopy

Photonics ◽

10.3390/photonics8020041 ◽

2021 ◽

Vol 8 (2) ◽

pp. 41

Author(s):

Najat Andam ◽

Siham Refki ◽

Hidekazu Ishitobi ◽

Yasushi Inouye ◽

Zouheir Sekkat

Keyword(s):

Refractive Index ◽

Optical Properties ◽

Surface Plasmon Resonance ◽

Surface Plasmon ◽

Spectroscopic Ellipsometry ◽

Plasmon Resonance ◽

Complex Refractive Index ◽

Resonance Spectroscopy ◽

Doped Polymers

The determination of optical constants (i.e., real and imaginary parts of the complex refractive index (nc) and thickness (d)) of ultrathin films is often required in photonics. It may be done by using, for example, surface plasmon resonance (SPR) spectroscopy combined with either profilometry or atomic force microscopy (AFM). SPR yields the optical thickness (i.e., the product of nc and d) of the film, while profilometry and AFM yield its thickness, thereby allowing for the separate determination of nc and d. In this paper, we use SPR and profilometry to determine the complex refractive index of very thin (i.e., 58 nm) films of dye-doped polymers at different dye/polymer concentrations (a feature which constitutes the originality of this work), and we compare the SPR results with those obtained by using spectroscopic ellipsometry measurements performed on the same samples. To determine the optical properties of our film samples by ellipsometry, we used, for the theoretical fits to experimental data, Bruggeman’s effective medium model for the dye/polymer, assumed as a composite material, and the Lorentz model for dye absorption. We found an excellent agreement between the results obtained by SPR and ellipsometry, confirming that SPR is appropriate for measuring the optical properties of very thin coatings at a single light frequency, given that it is simpler in operation and data analysis than spectroscopic ellipsometry.

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The complex refractive index of aerosols during LACE 98 as derived from the analysis of individual particles

Journal of Aerosol Science ◽

10.1016/s0021-8502(21)00309-8 ◽

2001 ◽

Vol 32 ◽

pp. 683-684

Author(s):

M. EBERT ◽

S. WEINBRUCH ◽

A. RAUSCH ◽

G. GORZAWSKI ◽

H. WEX ◽

...

Keyword(s):

Refractive Index ◽

Complex Refractive Index ◽

Individual Particles

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Solution of complex characteristic equation of LPFG sensors coated with complex refractive index double-layer films

2011 Second International Conference on Mechanic Automation and Control Engineering ◽

10.1109/mace.2011.5988832 ◽

2011 ◽

Author(s):

Zhengtian Gu ◽

Chuanlu Deng ◽

Jiangtao Zhang ◽

Yingcai Wu

Keyword(s):

Refractive Index ◽

Double Layer ◽

Characteristic Equation ◽

Complex Refractive Index ◽

Complex Characteristic

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Optimising the Complex Refractive Index Model for Estimating the Permittivity of Heterogeneous Concrete Models

Remote Sensing ◽

10.3390/rs13040723 ◽

2021 ◽

Vol 13 (4) ◽

pp. 723

Author(s):

Hossain Zadhoush ◽

Antonios Giannopoulos ◽

Iraklis Giannakis

Keyword(s):

Refractive Index ◽

Shape Factor ◽

Complex Refractive Index ◽

Fdtd Method ◽

Air Voids ◽

Water Fraction ◽

Index Model ◽

General Complex ◽

Ground Penetrating ◽

Fine Tune

Estimating the permittivity of heterogeneous mixtures based on the permittivity of their components is of high importance with many applications in ground penetrating radar (GPR) and in electrodynamics-based sensing in general. Complex Refractive Index Model (CRIM) is the most mainstream approach for estimating the bulk permittivity of heterogeneous materials and has been widely applied for GPR applications. The popularity of CRIM is primarily based on its simplicity while its accuracy has never been rigorously tested. In the current study, an optimised shape factor is derived that is fine-tuned for modelling the dielectric properties of concrete. The bulk permittivity of concrete is expressed with respect to its components i.e., aggregate particles, cement particles, air-voids and volumetric water fraction. Different combinations of the above materials are accurately modelled using the Finite-Difference Time-Domain (FDTD) method. The numerically estimated bulk permittivity is then used to fine-tune the shape factor of the CRIM model. Then, using laboratory measurements it is shown that the revised CRIM model over-performs the default shape factor and provides with more accurate estimations of the bulk permittivity of concrete.

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