Complex refractive index of aerosol samples

Mico, Silvana; Deda, Antoneta; Tsaousi, Eleni; Alushllari, Mirela; Pomonis, P.J.

doi:10.1063/1.5110120

Cited by 6 publications

(8 citation statements)

References 8 publications

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“…Figure 4 shows the calculated light intensity ratio of the uncoalesced bisphere particle and equivalent spherical particle as a function of monomer diameter and refractive index. Typically, organics have a refractive index of 1.4-1.7 (Flores et al, 2014;He et al, 2018;Nakayama et al, 2012;Moise et al, 2015), and sea salt has a refractive index of 1.51 (Bi et al, 2018), which span the range of most atmospheric aerosol types (Mico et al, 2019;Shepherd et al, 2018). Some secondary organic aerosol particles from monoterpenes such as limonene, α-humulene, and α-pinene have an imaginary part of the refractive index, k < 0.05 (Flores et al, 2014).…”

Section: Light-scattering Calculationsmentioning

confidence: 99%

Characterization of a modified printed optical particle spectrometer for high-frequency and high-precision laboratory and field measurements

et al. 2022

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Abstract. The printed optical particle spectrometer (POPS) is a lightweight, low-cost instrument for measurements of aerosol number concentrations and size distributions. This work reports on modifications of the Handix Scientific commercial version of the POPS to facilitate its use in multi-instrument aerosol sampling systems. The flow system is modified by replacing the internal pump with a needle valve and a vacuum pump. The instrument is integrated into closed-flow systems by routing the sheath flow from filtered inlet air. A high-precision multichannel analyzer (MCA) card is added to sample the analog pulse signal. The MCA card is polled at 10 Hz frequency using an external data acquisition system and improves upon the count-rate limitation associated with the POPS internal data acquisition system. The times required to change the concentration between 90 % and 10 % and vice versa for a step change in concentration were measured to be 0.17 and 0.41 s at a flow rate of 5 cm3 s−1. This yields a sampling frequency of ∼ 1–2 Hz, below which the amplitude of measured fluctuations is captured with > 70 % efficiency. The modified POPS was integrated into the dual tandem differential mobility analyzer system to explore the coalescence of dimer particles. Results show that the pulse-height response increases upon dimer coalescence. The magnitude of the increase is broadly consistent with the change in light-scattering amplitude predicted by the T-matrix method. It is anticipated that this modified version of the POPS will extend the utilization of the technique for a range of field and laboratory applications.

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Section: Light-scattering Calculationsmentioning

confidence: 99%

Characterization of a modified printed optical particle spectrometer for high-frequency and high-precision laboratory and field measurements

et al. 2022

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“…Furthermore, values of m I retrieved within the lower aerosol layer are compatible with those found for the submicron and coarse fractions of black carbon particles (0.0075 in Panchenko et al., 2012), which can result from combustion of coal, oil and oil‐shale. Observed values of m I are also compatible with mineral dust particles (0.006 in Mico et al., 2019, and Wang et al., 2021, and 0.0055 in Willoughby et al., 2017) and with smoke particles (0.008 in McMeeking, 2004).…”

Section: Resultsmentioning

confidence: 58%

“…Unfortunately, independent measurements of m R and m I from in‐situ sensors are not available. However, an indirect estimation of these quantities can be inferred from the compositional information available from the chemical sensor, supported by literature papers (McMeeking, 2004; Mico et al., 2019; Panchenko et al., 2012; Sekiyama et al., 2012; Wang et al., 2021; Willoughby et al., 2017; Zhao et al., 2020).…”

Section: Resultsmentioning

confidence: 85%

Measurements of Aerosol Size and Microphysical Properties: A Comparison Between Raman Lidar and Airborne Sensors

et al. 2022

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This manuscript compares measurements of aerosol size distributions and microphysical properties retrieved from the Raman lidar BASIL with those obtained from a series of aircraft sensors during HyMeX‐SOP1. The attention is focused on a measurement session on 02 October 2012, with BASIL measurements revealing the presence of a lower aerosol layer extending up to 3.3 km and an elevated layer extending from 3.6 to 4.6 km. Aerosol size distribution and microphysical properties are determined from multi‐wavelength particle backscattering and extinction profile measurements through a retrieval approach based on Tikhonov regularization. A good agreement is found between BASIL and the microphysical sensors' measurements for all considered aerosol size and microphysical properties. Specifically, BASIL and in‐situ volume concentration values are in the range 2–5 μm3 cm−3 in the lower layer and in the range 1–3.5 μm3 cm−3 in the upper layer. Values of the effective radius values from BASIL and the in‐situ sensors are in the range 0.2–0.6 μm in both the lower and upper layer. Aerosol size distributions are determined at 2.2, 2.8, 4 and 4.3 km, with a good agreement between the Raman lidar and the microphysical sensors at all considered heights. We combined these size and microphysical results with Lagrangian back‐trajectory analyses and chemical composition measurements. From this combination of datasets we conclude that aerosol particles below 3 km were probably originated by wildfires in North America and/or by anthropogenic activities in North‐Eastern Europe, while aerosols above 3 km were also probably originated by wildfires in North America.

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“…Decreasing N by 10% led to an almost 2-fold increase in k eff (Δ k eff = 0.011), whereas increasing N by the same fraction only slightly decreased k eff (Δ k eff = 0.002). Regardless of these sensitivities, the absolute value of k eff is almost an order of magnitude higher than that of nonabsorbing silica and much smaller (<5%) than k of absorbing materials such as graphene and soot at all λ considered. , …”

Section: Resultsmentioning

confidence: 90%

“…Regardless of these sensitivities, the absolute value of k eff is almost an order of magnitude higher than that of nonabsorbing silica and much smaller (<5%) than k of absorbing materials such as graphene and soot at all λ considered. 43,64 Previous studies have retrieved k for Martian dusts from observational data sets. Ockert-Bell and Bell created a model using Hapke theory (derives reflectance of a mixture using singly and multiply scattered light) and size distribution data from the Viking lander's scattering angle measurements to estimate the single-scattering albedo (ω o , the ratio of scattering to extinction) and retrieved k = 0.011 at λ = 500 nm and assuming an effective particle diameter of 3.7 μm.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Absorption Spectra of Martian Dust Simulants

Razafindrambinina

Asa-Awuku

Radney

et al. 2022

ACS Earth Space Chem.

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Understanding the Martian climate requires a detailed characterization of the optical properties of Martian dust as it is a ubiquitous component of the atmosphere. The continued improvement of Martian atmosphere observations motivates measurements of terrestrial simulants under controlled conditions to support field studies and computational modeling. This investigation demonstrates an in situ method to entrain and directly measure the absorption spectrum of six Martian dust simulants using photoacoustic spectroscopy. Measured size distributions and absorption cross sections (C abs) are used in Mie theory calculations to retrieve the effective imaginary component of the refractive index (k eff) of each sample while constraining the real component to n = 1.5, the refractive index of silica. The weakly absorbing simulants have k eff values ranging between 0.002 and 0.03 at a wavelength of 500 nm that are correlated with the mass fraction of iron oxides.

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Complex refractive index of aerosol samples

Cited by 6 publications

References 8 publications

Characterization of a modified printed optical particle spectrometer for high-frequency and high-precision laboratory and field measurements

Characterization of a modified printed optical particle spectrometer for high-frequency and high-precision laboratory and field measurements

Measurements of Aerosol Size and Microphysical Properties: A Comparison Between Raman Lidar and Airborne Sensors

Absorption Spectra of Martian Dust Simulants

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