Complex Refractive Indices of Aerosols Retrieved by Continuous Wave-Cavity Ring Down Aerosol Spectrometer

Lang‐Yona, Naama; Rudich, Yinon; Segre, Enrico; Dinar, E.; Abo-Riziq, Ali

doi:10.1021/ac8017789

Cited by 88 publications

(154 citation statements)

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(112 reference statements)

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“…The CRD-AS system was described in details elsewhere (Dinar et al, 2008;Lang-Yona et al, 2009;Abo Riziq et al, 2007. Briefly, a pulsed laser light of ∼1 mJ at λ = 355 nm is injected into a cavity containing two highly reflective mirrors (reflectivity, R = 99.9) where it undergoes multiple passes.…”

Section: Crd-as Systemmentioning

confidence: 99%

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The optical, physical and chemical properties of the products of glyoxal uptake on ammonium sulfate seed aerosols

et al. 2011

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Abstract. The heterogeneous reaction between gas phase glyoxal and ammonium sulfate (AS) aerosols, a proxy for inorganic atmospheric aerosol, was studied in terms of the dependence of the optical, physical and chemical properties of the product aerosols on initial particle size and ambient relative humidity (RH). Our experiments imitate an atmospheric scenario of a dry particle hydration at ambient RH conditions in the presence of glyoxal gas followed by efflorescence due to decrease of the ambient RH. The reactions were studied under different RH conditions, starting from dry conditions (∼20 % RH) and up to 90 % RH, covering conditions prevalent in many atmospheric environments, and followed by consequent drying of the reacted particles before their analysis by the aerosol mass spectrometer (AMS), cavity ring down (CRD) and scanning mobility particle sizer (SMPS) systems. At λ = 355 nm, the reacted aerosols demonstrate a substantial growth in optical extinction cross section, as well as in mobility diameter under a broad range of RH values (35-90 %). The ratio of the product aerosol to seed aerosol geometric cross section reached up to ∼3.5, and the optical extinction cross-section up to ∼250. The reactions show a trend of increasing physical and optical growth with decreasing seed aerosol size, from 100 nm to 300 nm, as well as with decreasing RH values from 90 % to ∼40 %. Optically inactive aerosols, at the limit of the Mie range (100 nm diameter) become optically active as they grow due to the reaction. AMS analyses of the reaction of 300 nm AS at RH values of 50 %, 75 % and 90 % show that the main products of the reaction are glyoxal oligomers, formed by acetal formation in the presence of AS. In addition, imidaCorrespondence to: Y. Rudich (yinon.rudich@weizmann.ac.il) zole formation, which is a minor channel, is observed for all reactions, yielding a product which absorbs at λ = 290 nm, with possible implications on the radiative properties of the product aerosols. The ratio of absorbing substances (C-N compounds, including imidazoles) increases with increasing RH value. A core/shell model used for the investigation of the optical properties of the reaction products of AS with gas phase glyoxal, shows that the refractive index (RI) of the reaction products are n = 1.68(±0.10) + 0.01(±0.02) at 50 % RH and n = 1.65(±0.06) + 0.02(±0.01) at 75 % RH at 355 nm. The observed increase in the ratio of the absorbing substances is not indicated in the imaginary part of the products at RH 50 % and 75 %. A further increase in the ratio of absorbing substances and a resulting increase in the imaginary part of the RI at higher RH values is expected, and may become even more substantial after longer reaction times, possibly in cloud or fog droplets. This study shows that the reaction of abundant substances present in atmospheric aerosols, such as AS, and gas phase glyoxal alters the aerosols' optical, physical and chemical properties and may have implications on the radiative effect of these aerosols.

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Section: Crd-as Systemmentioning

confidence: 99%

“…Using the particle number concentration, the extinction cross section (σ ext ) at a specific wavelength can be calculated (Eq. 2) (Lang-Yona et al, 2009;Pettersson, 2004;Abo Riziq et al, 2007.…”

Section: Crd-as Systemmentioning

confidence: 99%

The optical, physical and chemical properties of the products of glyoxal uptake on ammonium sulfate seed aerosols

et al. 2011

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“…To retrieve the RI from the CRD-AS measurements, the extinction efficiency of the humidified aerosols (Q ext-%RH ) was calculated from the measured GF and the extinction coefficient at every diameter. By knowing the value of Q ext at different diameters for internally mixed aerosols, a refractive index can be retrieved (Lang-Yona et al, 2009;Pettersson et al, 2004;Abo Riziq et al, 2007). Figure 4 shows two examples of the results of the complex RI derivation and comparison performed.…”

Section: Optical Growth Of Humidified Absorbing Aerosolsmentioning

confidence: 99%

Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

et al. 2012

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Abstract. One of the major uncertainties in the understanding of Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. Aerosols exposed to high humidity will change their chemical, physical, and optical properties due to their increased water content. To model hydrated aerosols, atmospheric chemistry and climate models often use the volume weighted mixing rule to predict the complex refractive index (RI) of aerosols when they interact with high relative humidity, and, in general, assume homogeneous mixing. This study explores the validity of these assumptions. A humidified cavity ring down aerosol spectrometer (CRD-AS) and a tandem hygroscopic DMA (differential mobility analyzer) are used to measure the extinction coefficient and hygroscopic growth factors of humidified aerosols, respectively. The measurements are performed at 80 % and 90 %RH at wavelengths of 532 nm and 355 nm using size-selected aerosols with different degrees of absorption; from purely scattering to highly absorbing particles. The ratio of the humidified to the dry extinction coefficients (f RH ext (%RH, Dry)) is measured and compared to theoretical calculations based on Mie theory. Using the measured hygroscopic growth factors and assuming homogeneous mixing, the expected RIs using the volume weighted mixing rule are compared to the RIs derived from the extinction measurements.We found a weak linear dependence or no dependence of f RH(%RH, Dry) with size for hydrated absorbing aerosols in contrast to the non-monotonically decreasing behavior with size for purely scattering aerosols. No discernible difference could be made between the two wavelengths used. Less than 7 % differences were found between the real parts of the complex refractive indices derived and those calculated using the volume weighted mixing rule, and the imaginary parts had up to a 20 % difference. However, for substances with growth factor less than 1.15 the volume weighted mixing rule assumption needs to be taken with caution as the imaginary part of the complex RI can be underestimated.

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“…In particular, in situ measurements of the extinction and other optical parameters of atmospheric aerosols are crucial, and these require real-time, accurate, and sensitive techniques that can detect the ambient aerosols and their rapid temporal and spatial changes. Recent years have seen a rapid rise in the use of cavity ringdown spectroscopy (CRDS), a sensitive and direct optical extinction technique, to determine the optical properties of both laboratory generated and atmospheric ambient aerosols [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17].…”

mentioning

confidence: 99%

“…Many more studies have been subsequently carried out to measure the optical extinction of aerosol particles using CRDS [6][7][8][9][10]. Most of these pervious works were based on using either a pulsed YAG laser, which is relatively bulky and limited to only 355, 532 or 1064 nm laser radiation [12][13][14], or a pulsed tunable dye laser, which is cumbersome and not suitable for field study [15]. The cw-CRDS using narrow linewidth diode laser in visible (690 nm) [16] and near-IR (1550 and 1650 nm) [16,17] was also utilized for the aerosol extinction measurements.…”

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confidence: 99%

Measurement of aerosol optical extinction using diode laser cavity ringdown spectroscopy

Liu

Zhang

2013

Chin. Sci. Bull.

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Accurate measurement of optical extinction of atmospheric aerosols is important for quantifying the direct climate effects of aerosols. A portable cavity ringdown spectrometer utilizing a modulated multimode blue diode laser (linewidth ~0.2 nm) is developed to measure the aerosol optical extinction. Laboratory generated ammonia sulfate particles (<1 μm in diameter) are characterized, with good agreements between the experimental measurements and Mie theory calculations. An optical extinction detection sensitivity of 0.24 Mm −1 (1σ) is achieved. Measurements of ambient aerosols are also carried out. This study demonstrates the feasibility of a compact, multimode diode laser cavity ringdown spectrometer for sensitive measurements of the optical extinction of atmospheric aerosols. aerosol, optical extinction, spectroscopy Citation:Liu Y D, Zhang J S. Measurement of aerosol optical extinction using diode laser cavity ringdown spectroscopy.

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Complex Refractive Indices of Aerosols Retrieved by Continuous Wave-Cavity Ring Down Aerosol Spectrometer

Cited by 88 publications

References 50 publications

The optical, physical and chemical properties of the products of glyoxal uptake on ammonium sulfate seed aerosols

The optical, physical and chemical properties of the products of glyoxal uptake on ammonium sulfate seed aerosols

Absorbing aerosols at high relative humidity: linking hygroscopic growth to optical properties

Measurement of aerosol optical extinction using diode laser cavity ringdown spectroscopy

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