scholarly journals Experimental study of H<sub>2</sub>SO<sub>4</sub> aerosol nucleation at high ionization levels

2017 ◽  
Author(s):  
Maja Tomicic ◽  
Martin Bødker Enghoff ◽  
Henrik Svensmark
Keyword(s):  
Sulphuric Acid ◽  
Cluster Size ◽  
Gamma Ray ◽  
Reaction Chamber ◽  
Critical Cluster ◽  
H2so4 Concentration ◽  
Ion Concentrations ◽  
High Ionization ◽  
Direct Measurements ◽  
Mobility Diameter

Abstract. One hundred and ten direct measurements of aerosol nucleation rate at high ionization levels were performed in an 8 m3 reaction chamber. Neutral and ion-induced particle formation from sulphuric acid (H2SO4) as a function of ionization and H2SO4 concentration was studied. Other species that could participate in the nucleation were not measured. The measurements extend the parameter space of measurements described by (Dunne, 2016) (at T = 295 K and RH = 38 %) by expanding to lower H2SO4 concentrations (4x106–3x107 cm−3) and higher ion concentrations (1700–19000 cm−3). The ion concentrations, which correspond to levels caused by a nearby supernova, were achieved with gamma ray sources. Nucleation rates were directly measured with a particle size magnifier (PSM Airmodus A10) at a size close to critical cluster size (mobility diameter of ~ 1.4 nm) and formation rates at mobility diameter of ~ 4 nm were measured with a CPC (TSI model 3775). The measurements show that nucleation increases by around a factor of five when the ionization increases from background to supernova levels under fixed gas conditions. The results expand the parametrization from (Dunne, 2016) to lower sulphuric acid concentrations and higher ion concentrations.

scholarly journals Experimental study of H<sub>2</sub>SO<sub>4</sub> aerosol nucleation at high ionization levels

2018 ◽  
Vol 18 (8) ◽  
pp. 5921-5930 ◽  
Author(s):  
Maja Tomicic ◽  
Martin Bødker Enghoff ◽  
Henrik Svensmark
Keyword(s):  
Sulfuric Acid ◽  
Gamma Ray ◽  
Reaction Chamber ◽  
Critical Cluster ◽  
H2so4 Concentration ◽  
Ion Concentrations ◽  
High Ionization ◽  
Direct Measurements ◽  
Mobility Diameter ◽  
Order Of Magnitude

Abstract. One hundred and ten direct measurements of aerosol nucleation rate at high ionization levels were performed in an 8 m3 reaction chamber. Neutral and ion-induced particle formation from sulfuric acid (H2SO4) was studied as a function of ionization and H2SO4 concentration. Other species that could have participated in the nucleation, such as NH3 or organic compounds, were not measured but assumed constant, and the concentration was estimated based on the parameterization by Gordon et al. (2017). Our parameter space is thus [H2SO4] =4×106-3×107 cm−3, [NH3+ org] = 2.2 ppb, T=295 K, RH = 38 %, and ion concentrations of 1700–19 000 cm−3. The ion concentrations, which correspond to levels caused by a nearby supernova, were achieved with gamma ray sources. Nucleation rates were directly measured with a particle size magnifier (PSM Airmodus A10) at a size close to critical cluster size (mobility diameter of ∼ 1.4 nm) and formation rates at a mobility diameter of ∼ 4 nm were measured with a CPC (TSI model 3775). The measurements show that nucleation increases by around an order of magnitude when the ionization increases from background to supernova levels under fixed gas conditions. The results expand the parameterization presented in Dunne et al. (2016) and Gordon et al. (2017) (for [NH3+org] = 2.2 ppb and T=295 K) to lower sulfuric acid concentrations and higher ion concentrations. The results make it possible to expand the parameterization presented in Dunne et al. (2016) and Gordon et al. (2017) to higher ionization levels.

scholarly journals Nucleation of Ga droplets self-assembly on GaAs(111)A substrates

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Artur Tuktamyshev ◽  
Alexey Fedorov ◽  
Sergio Bietti ◽  
Stefano Vichi ◽  
Riccardo Tambone ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Size Distribution ◽  
Self Assembly ◽  
Cluster Size ◽  
Droplet Size Distribution ◽  
Local Environment ◽  
The Self ◽  
Critical Cluster ◽  
Droplet Nucleation ◽  
High Degree

AbstractWe investigated the nucleation of Ga droplets on singular GaAs(111)A substrates in the view of their use as the seeds for the self-assembled droplet epitaxial quantum dots. A small critical cluster size of 1–2 atoms characterizes the droplet nucleation. Low values of the Hopkins-Skellam index (as low as 0.35) demonstrate a high degree of a spatial order of the droplet ensemble. Around $$350\,^{\circ }\hbox {C}$$ 350 ∘ C the droplet size distribution becomes bimodal. We attribute this observation to the interplay between the local environment and the limitation to the adatom surface diffusion introduced by the Ehrlich–Schwöbel barrier at the terrace edges.

A study of the critical cluster size for water monolayer clusters on a model AgI basal substratea)

1983 ◽  
Vol 78 (1) ◽  
pp. 420-423 ◽  
Author(s):  
Richard C. Ward ◽  
Barbara N. Hale ◽  
Sergio Terrazas
Keyword(s):  
Cluster Size ◽  
Critical Cluster ◽  
Critical Cluster Size

scholarly journals Performance of diethylene glycol-based particle counters in the sub-3 nm size range

2013 ◽  
Vol 6 (7) ◽  
pp. 1793-1804 ◽  
Author(s):  
D. Wimmer ◽  
K. Lehtipalo ◽  
A. Franchin ◽  
J. Kangasluoma ◽  
F. Kreissl ◽  
...  
Keyword(s):  
High Resolution ◽  
Laminar Flow ◽  
Nucleation Rate ◽  
Diethylene Glycol ◽  
Cluster Size ◽  
Detection Efficiency ◽  
Working Fluid ◽  
Critical Cluster ◽  
Mixing Ratios ◽  
Critical Cluster Size

Abstract. When studying new particle formation, the uncertainty in determining the "true" nucleation rate is considerably reduced when using condensation particle counters (CPCs) capable of measuring concentrations of aerosol particles at sizes close to or even at the critical cluster size (1–2 nm). Recently, CPCs able to reliably detect particles below 2 nm in size and even close to 1 nm became available. Using these instruments, the corrections needed for calculating nucleation rates are substantially reduced compared to scaling the observed formation rate to the nucleation rate at the critical cluster size. However, this improved instrumentation requires a careful characterization of their cut-off size and the shape of the detection efficiency curve because relatively small shifts in the cut-off size can translate into larger relative errors when measuring particles close to the cut-off size. Here we describe the development of two continuous-flow CPCs using diethylene glycol (DEG) as the working fluid. The design is based on two TSI 3776 counters. Several sets of measurements to characterize their performance at different temperature settings were carried out. Furthermore, two mixing-type particle size magnifiers (PSM) A09 from Airmodus were characterized in parallel. One PSM was operated at the highest mixing ratio (1 L min−1 saturator flow), and the other was operated in a scanning mode, where the mixing ratios are changed periodically, resulting in a range of cut-off sizes. The mixing ratios are determined by varying the saturator flow, where the aerosol flow stays constant at 2.5 L min−1. Different test aerosols were generated using a nano-differential mobility analyser (nano-DMA) or a high-resolution DMA, to obtain detection efficiency curves for all four CPCs. One calibration setup included a high-resolution mass spectrometer (APi-TOF) for the determination of the chemical composition of the generated clusters. The lowest cut-off sizes were achieved with negatively charged ammonium sulfate clusters, resulting in cut-offs of 1.4 nm for the laminar flow CPCs and 1.2 and 1.1 nm for the PSMs. A comparison of one of the laminar-flow CPCs and one of the PSMs measuring ambient and laboratory air showed good agreement between the instruments.

THE INFLUENCE OF A CRITICAL SIZE ON THE SCALING BEHAVIOR OF CLUSTERS COALESCENCE

1999 ◽  
Vol 13 (18) ◽  
pp. 2397-2404 ◽  
Author(s):  
GUOCE ZHUANG ◽  
XIAOBIN ZHU ◽  
WEI WANG
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Cluster Size ◽  
Critical Size ◽  
Simulation Method ◽  
Monte Carlo Simulation Method ◽  
Critical Cluster ◽  
Cluster Aggregation ◽  
Long Time ◽  
Average Size

By introducing a critical cluster size N c , the irreversible and reversible cluster–cluster aggregation are studied with Monte Carlo simulation method. In a long time limit the average size of cluster <S>∞ reaches its stationary value which depends on the critical size N c and the breakup constant k. Our results indicate that in the presence of critical size the critical exponent y, which is defined as <S(k,∞)>~k-y, increases as the critical size increases and is lower than the value of (α+ξ+2)-1, where the exponents α and ξ associate with the detachment and attachment of clusters.

Critical cluster size cannot in practice be determined by slope analysis in atmospherically relevant applications

2014 ◽  
Vol 77 ◽  
pp. 127-144 ◽  
Author(s):  
Oona Kupiainen-Määttä ◽  
Tinja Olenius ◽  
Hannele Korhonen ◽  
Jussi Malila ◽  
Miikka Dal Maso ◽  
...  
Keyword(s):  
Cluster Size ◽  
Critical Cluster ◽  
Slope Analysis ◽  
Critical Cluster Size ◽  
Atmospherically Relevant

scholarly journals Constraints on the optical-IR extragalactic background from γ-ray absorption studies

2011 ◽  
Vol 7 (S284) ◽  
pp. 420-428 ◽  
Author(s):  
Luigi Costamante
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Background Light ◽  
Radiation Fields ◽  
Direct Measurements ◽  
Absorption Studies ◽  
Diffuse Background ◽  
Very High Energy ◽  
Tev Gamma Rays ◽  
Very High

AbstractVery high energy (VHE ≳0.1 TeV) gamma-rays from extragalactic sources, interacting by γ-γ collisions with diffuse intergalactic radiation fields, provide an alternative way to constrain the diffuse background light, completely independent of direct measurements. The limits depend however on our knowledge of the physics of the gamma-ray sources. After clarifying the interplay between background light and VHE spectra, I summarize the extent and validity of the obtainable limits, and where future improvements can be expected.

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