Collision-Based Ionization: Bridging the Gap between Chemical Ionization and Aerosol Particle Diffusion Charging

Premnath, Vinay; Oberreit, Derek R.; Hogan, Christopher J.

doi:10.1080/02786826.2011.556683

Cited by 16 publications

(5 citation statements)

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“…We believe the primary sources of uncertainty in calculated values of N are associated with uncertainties in f detection and f charging , both of which become more uncertain as particle size decreases and may depend on composition (O'Dowd et al, 2002;Iida et al, 2009;Jiang et al, 2011a;Premnath et al, 2011). We have measured f detection in the laboratory for particles of known composition (NaCl, Ag, and tetra-alkyl ammonium ions N + [C n H 2n+1 ] 4 ).…”

Section: C21 Nccn Eventmentioning

confidence: 99%

Size and time-resolved growth rate measurements of 1 to 5 nm freshly formed atmospheric nuclei

et al. 2012

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Abstract. This study presents measurements of size and time-resolved particle diameter growth rates for freshly nucleated particles down to 1 nm geometric diameter. Novel data analysis methods were developed, de-coupling for the first time the size and time-dependence of particle growth rates by fitting the aerosol general dynamic equation to size distributions obtained at an instant in time. Size distributions of freshly nucleated total aerosol (neutral and charged) were measured during two intensive measurement campaigns in different environments (Atlanta, GA and Boulder, CO) using a recently developed electrical mobility spectrometer with a diethylene glycol-based ultrafine condensation particle counter as the particle detector. One new particle formation (NPF) event from each campaign was analyzed in detail. At a given instant in time during the NPF event, sizeresolved growth rates were obtained directly from measured size distributions and were found to increase approximately linearly with particle size from ∼1 to 3 nm geometric diameter, increasing from 5.5 ± 0.8 to 7.6 ± 0.6 nm h −1 in Atlanta (13:00) and from 5.6 ± 2 to 27 ± 5 nm h −1 in Boulder (13:00). The resulting growth rate enhancement , defined as the ratio of the observed growth rate to the growth rate due to the condensation of sulfuric acid only, was found to increase approximately linearly with size from ∼1 to 3 nm geometric diameter. For the presented NPF events, values for had lower limits that approached ∼1 at 1.2 nm geometric diameter in Atlanta and ∼3 at 0.8 nm geometric diameter in Boulder, and had upper limits that reached 8.3 at 4.1 nm geometric diameter in Atlanta and 25 at 2.7 nm geometric diameter in Boulder. Nucleated particle survival probability calculations comparing the effects of constant and size-dependent growth indicate that neglecting the strong dependence of growth rate on size from 1 to 3 nm observed in this study could lead to a significant overestimation of CCN survival probability.

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Section: C21 Nccn Eventmentioning

confidence: 99%

Size and time-resolved growth rate measurements of 1 to 5 nm freshly formed atmospheric nuclei

et al. 2012

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“…Gas phase collisions of charged particles with ions as well as with other charged particles play an important role in governing the behavior of aerosols [1][2][3][4][5][6][7][8] and dusty plasmas [9][10][11][12][13][14][15][16][17] , with particle charge distributions in these systems dependent on the rates at which these collisions occur. Determination of the collision rates of charged entities is therefore essential in characterizing the properties and behavior of aerosol and dusty plasma particles.…”

Section: Introductionmentioning

confidence: 99%

Coulomb-influenced collisions in aerosols and dusty plasmas

Gopalakrishnan

Hogan

2012

Phys. Rev. E

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In aerosol and dusty plasma systems, the behavior of suspended particles (grains) is often strongly influenced by collisions occurring between ions and particles, as well as between particles themselves. In determining the collision kernel or collision rate coefficient for such charged entities, complications arise in that the collision process can be completely described neither by continuum transport mechanics nor by free molecular (ballistic) mechanics; that is, collisions are transition regime processes. Further, both the thermal energy and the potential energy between colliding entities can strongly influence the collision rate and must be considered. Flux-matching theory, originally developed by Fuchs, is frequently applied for calculation of collision rate coefficients under these circumstances. However, recent work suggests that crucial assumptions in flux-matching theory are not appropriate to describe transition regime collisions in the presence of potential interactions. Here, we combine dimensional analysis and mean first passage time calculations to infer the collision kernel between dilute charged entities suspended in a light background gas at thermal equilibrium. The motion of colliding entities is described by a Langevin equation, and Coulombic interactions are considered. It is found that the dimensionless collision kernel for these conditions, H, is a function of the diffusive Knudsen number, Kn(D) (in contrast to the traditional Knudsen number), and the potential energy to thermal energy ratio, Ψ(E). For small and large Kn(D), it is found that the dimensionless collision kernels inferred from mean first passage time calculations collapse to the appropriate continuum and free molecular limiting forms, respectively. Further, for repulsive collisions (Ψ(E) negative) or attractive collisions with Ψ(E)<0.5, calculated results are in excellent agreement with flux-matching theory predictions, and the dimensionless collision kernel can be determined conveniently via use of the H(Kn(D)) relationship found for hard-sphere collisions with modified definitions of H and Kn(D) to account for potential energy. However, for Ψ(E)>0.5, it is found that flux-matching theory predictions substantially underestimate the collision kernel. We find that the collision process in this regime is governed by the minimum of Kn(D) and Kn(Ψ) (Kn(Ψ) = 3Kn(D)/2Ψ(E)), and based on calculations, propose a function H(Kn(D), Kn(Ψ)) for collision kernel evaluation. The situations for which Ψ(E)>0.5 apply to singly charged nanoparticles and multiply charged submicrometer and supermicrometer particles, and are thus prevalent in both aerosol and dusty plasma environments.

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“…Alonso et al (1997) presented experimental data on bipolar charging probabilities of sub-3 nm particles, which underestimates the charging probability by up to a factor of 2 from the Fuchs diffusion based charging theory. Premnath et al (2011) studied the charge transfer from the small clusters back to the vapor molecules, which is not taken into account in the regularly used diffusion charging theories, and found out that the charge transfer is dependent on both cluster size and chemistry. Due to a lack of experimental data the charge transfer processes at cluster level are not well understood, and these effects are often not discussed as a source of uncertainty in the sub-10 nm particle concentrations measurements.…”

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confidence: 99%

On the sources of uncertainty in the sub-3 nm particle concentration measurement

Kangasluoma

Kontkanen

2017

Journal of Aerosol Science

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The number of experiments characterizing sub-3 nm aerosol particle dynamics has increased significantly over the recent years. In these experiments, it is essential to know/determine size resolved particle number concentrations accurately. Despite particle concentration measurement being relatively simple experiment, it can contain large uncertainties from various sources in the sub-3 nm size range. In this study we aim to identify and examine some of these sources. We simulated four different condensation particle counters (CPCs) (TSI 3777, ADI vWCPC, Airmodus A11 and an ideal CPC with d50 (lowest detection threshold) of 1.5 nm) and one differential mobility analyzer (DMA) (TSI nano DMA) and study the resulting uncertainties when using them to measure three different particle size distributions. First, we show that Poisson uncertainty √N/N represents the statistical uncertainty in all CPC and DMPS counting experiments. Second, the state-of-the-art DMA-CPC particle sizing system is examined with respect to counting statistics. Third, the performance of the instruments is assumed to be well-known, and instrumental non-idealities and the inversion routine are assessed. Fourth, ±0.5 nm offset is inserted to the CPC d50, and its effect on the measured particle concentration is examined. Our results highlight the importance of knowing the CPC d50 accurately to narrow down the particle concentration uncertainty. Furthermore, the results show that the current DMA-CPC measurements are subject to considerable counting uncertainty in low particle concentration environments. Based on the analysis we summarize suggestions for further research and instrumental development for more accurate sub-3 nm particle concentration measurements in the future. 1 Introduction In recent years, great efforts have been made to understand the formation and growth of sub-3 nm particles in the atmosphere (

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Collision-Based Ionization: Bridging the Gap between Chemical Ionization and Aerosol Particle Diffusion Charging

Cited by 16 publications

References 50 publications

Size and time-resolved growth rate measurements of 1 to 5 nm freshly formed atmospheric nuclei

Size and time-resolved growth rate measurements of 1 to 5 nm freshly formed atmospheric nuclei

Coulomb-influenced collisions in aerosols and dusty plasmas

On the sources of uncertainty in the sub-3 nm particle concentration measurement

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