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Binary nucleation of sulphuric acid-water particles is expected to be an important process in the free troposphere at low temperatures. SAWNUC (Sulphuric Acid Water Nucleation) is a model of binary nucleation that is based on laboratory measurements of the binding energies of sulphuric acid and water in charged and neutral clusters. Predictions of SAWNUC are compared for the first time comprehensively with experimental binary nucleation data from the CLOUD chamber at European Organization for Nuclear Research. The experimental measurements span a temperature range of 208–292 K, sulphuric acid concentrations from 1·106 to 1·109 cm−3, and distinguish between ion-induced and neutral nucleation. Good agreement, within a factor of 5, is found between the experimental and modeled formation rates for ion-induced nucleation at 278 K and below and for neutral nucleation at 208 and 223 K. Differences at warm temperatures are attributed to ammonia contamination which was indicated by the presence of ammonia-sulphuric acid clusters, detected by an Atmospheric Pressure Interface Time of Flight (APi-TOF) mass spectrometer. APi-TOF measurements of the sulphuric acid ion cluster distributions (math formula with i = 0, 1, ..., 10) show qualitative agreement with the SAWNUC ion cluster distributions. Remaining differences between the measured and modeled distributions are most likely due to fragmentation in the APi-TOF. The CLOUD results are in good agreement with previously measured cluster binding energies and show the SAWNUC model to be a good representation of ion-induced and neutral binary nucleation of sulphuric acid-water clusters in the middle and upper troposphere.

The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

Las palabras que revelan conceptos esenciales y situaciones fundamentales de la teoría y de la práctica jurídica y política no siempre tienen el mismo significado, sino que adquieren significados diferentes con relación a las diversas configuraciones históricas y geográficas de la sociedad civil y de la sociedad política. Lo mismo ocurre con el principio de legalidad y con el concepto de legalidad con este relacionado. En este artículo, queremos esbozar un cuadro del cambio del concepto de legalidad con referencia a la evolución de la forma de Estado –de Estado de derecho a Estado social– y al Estado constitucional. La última metamorfosis de la legalidad parece destacar la pérdida o, por lo menos, una crisis profunda de elementos fundamentales –antes que todo, el elemento de la certeza del derecho– que habían caracterizado la estructura y los ideales del concepto tradicional de legalidad., The words expressing essential concepts and fundamental ideas about legal and political theory and practice do not always recur with the same meaning, but they assume a different meaning depending on the different historical and geographical configurations of the civil and political society. The same thing is for the rule of law and for the relative concept of legality. Here, we want to give a hint of how the concept of legality has changed with reference to the evolution of the form of the State, from the legal State to the social State and, finally, to the constitutional State. The last metamorphosis of legality seems to show the loss, or at least, a deep crisis of fundamental elements, first of all the certainty of law, which had marked the structure and the ideals of the traditional concept of legality.

Las palabras que revelan conceptos esenciales y situaciones fundamentales de la teoría y de la práctica jurídica y política no siempre tienen el mismo significado, sino que adquieren significados diferentes con relación a las diversas configuraciones históricas y geográficas de la sociedad civil y de la sociedad política. Lo mismo ocurre con el principio de legalidad y con el concepto de legalidad con este relacionado. En este artículo, queremos esbozar un cuadro del cambio del concepto de legalidad con referencia a la evolución de la forma de Estado –de Estado de derecho a Estado social– y al Estado constitucional. La última metamorfosis de la legalidad parece destacar la pérdida o, por lo menos, una crisis profunda de elementos fundamentales –antes que todo, el elemento de la certeza del derecho– que habían caracterizado la estructura y los ideales del concepto tradicional de legalidad., The words expressing essential concepts and fundamental ideas about legal and political theory and practice do not always recur with the same meaning, but they assume a different meaning depending on the different historical and geographical configurations of the civil and political society. The same thing is for the rule of law and for the relative concept of legality. Here, we want to give a hint of how the concept of legality has changed with reference to the evolution of the form of the State, from the legal State to the social State and, finally, to the constitutional State. The last metamorphosis of legality seems to show the loss, or at least, a deep crisis of fundamental elements, first of all the certainty of law, which had marked the structure and the ideals of the traditional concept of legality.

Las palabras que revelan conceptos esenciales y situaciones fundamentales de la teoría y de la práctica jurídica y política no siempre tienen el mismo significado, sino que adquieren significados diferentes con relación a las diversas configuraciones históricas y geográficas de la sociedad civil y de la sociedad política. Lo mismo ocurre con el principio de legalidad y con el concepto de legalidad con este relacionado. En este artículo, queremos esbozar un cuadro del cambio del concepto de legalidad con referencia a la evolución de la forma de Estado –de Estado de derecho a Estado social– y al Estado constitucional. La última metamorfosis de la legalidad parece destacar la pérdida o, por lo menos, una crisis profunda de elementos fundamentales –antes que todo, el elemento de la certeza del derecho– que habían caracterizado la estructura y los ideales del concepto tradicional de legalidad., The words expressing essential concepts and fundamental ideas about legal and political theory and practice do not always recur with the same meaning, but they assume a different meaning depending on the different historical and geographical configurations of the civil and political society. The same thing is for the rule of law and for the relative concept of legality. Here, we want to give a hint of how the concept of legality has changed with reference to the evolution of the form of the State, from the legal State to the social State and, finally, to the constitutional State. The last metamorphosis of legality seems to show the loss, or at least, a deep crisis of fundamental elements, first of all the certainty of law, which had marked the structure and the ideals of the traditional concept of legality.

The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

Las palabras que revelan conceptos esenciales y situaciones fundamentales de la teoría y de la práctica jurídica y política no siempre tienen el mismo significado, sino que adquieren significados diferentes con relación a las diversas configuraciones históricas y geográficas de la sociedad civil y de la sociedad política. Lo mismo ocurre con el principio de legalidad y con el concepto de legalidad con este relacionado. En este artículo, queremos esbozar un cuadro del cambio del concepto de legalidad con referencia a la evolución de la forma de Estado –de Estado de derecho a Estado social– y al Estado constitucional. La última metamorfosis de la legalidad parece destacar la pérdida o, por lo menos, una crisis profunda de elementos fundamentales –antes que todo, el elemento de la certeza del derecho– que habían caracterizado la estructura y los ideales del concepto tradicional de legalidad., The words expressing essential concepts and fundamental ideas about legal and political theory and practice do not always recur with the same meaning, but they assume a different meaning depending on the different historical and geographical configurations of the civil and political society. The same thing is for the rule of law and for the relative concept of legality. Here, we want to give a hint of how the concept of legality has changed with reference to the evolution of the form of the State, from the legal State to the social State and, finally, to the constitutional State. The last metamorphosis of legality seems to show the loss, or at least, a deep crisis of fundamental elements, first of all the certainty of law, which had marked the structure and the ideals of the traditional concept of legality.

Las palabras que revelan conceptos esenciales y situaciones fundamentales de la teoría y de la práctica jurídica y política no siempre tienen el mismo significado, sino que adquieren significados diferentes con relación a las diversas configuraciones históricas y geográficas de la sociedad civil y de la sociedad política. Lo mismo ocurre con el principio de legalidad y con el concepto de legalidad con este relacionado. En este artículo, queremos esbozar un cuadro del cambio del concepto de legalidad con referencia a la evolución de la forma de Estado –de Estado de derecho a Estado social– y al Estado constitucional. La última metamorfosis de la legalidad parece destacar la pérdida o, por lo menos, una crisis profunda de elementos fundamentales –antes que todo, el elemento de la certeza del derecho– que habían caracterizado la estructura y los ideales del concepto tradicional de legalidad., The words expressing essential concepts and fundamental ideas about legal and political theory and practice do not always recur with the same meaning, but they assume a different meaning depending on the different historical and geographical configurations of the civil and political society. The same thing is for the rule of law and for the relative concept of legality. Here, we want to give a hint of how the concept of legality has changed with reference to the evolution of the form of the State, from the legal State to the social State and, finally, to the constitutional State. The last metamorphosis of legality seems to show the loss, or at least, a deep crisis of fundamental elements, first of all the certainty of law, which had marked the structure and the ideals of the traditional concept of legality.

Las palabras que revelan conceptos esenciales y situaciones fundamentales de la teoría y de la práctica jurídica y política no siempre tienen el mismo significado, sino que adquieren significados diferentes con relación a las diversas configuraciones históricas y geográficas de la sociedad civil y de la sociedad política. Lo mismo ocurre con el principio de legalidad y con el concepto de legalidad con este relacionado. En este artículo, queremos esbozar un cuadro del cambio del concepto de legalidad con referencia a la evolución de la forma de Estado –de Estado de derecho a Estado social– y al Estado constitucional. La última metamorfosis de la legalidad parece destacar la pérdida o, por lo menos, una crisis profunda de elementos fundamentales –antes que todo, el elemento de la certeza del derecho– que habían caracterizado la estructura y los ideales del concepto tradicional de legalidad., The words expressing essential concepts and fundamental ideas about legal and political theory and practice do not always recur with the same meaning, but they assume a different meaning depending on the different historical and geographical configurations of the civil and political society. The same thing is for the rule of law and for the relative concept of legality. Here, we want to give a hint of how the concept of legality has changed with reference to the evolution of the form of the State, from the legal State to the social State and, finally, to the constitutional State. The last metamorphosis of legality seems to show the loss, or at least, a deep crisis of fundamental elements, first of all the certainty of law, which had marked the structure and the ideals of the traditional concept of legality.

The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.

Las palabras que revelan conceptos esenciales y situaciones fundamentales de la teoría y de la práctica jurídica y política no siempre tienen el mismo significado, sino que adquieren significados diferentes con relación a las diversas configuraciones históricas y geográficas de la sociedad civil y de la sociedad política. Lo mismo ocurre con el principio de legalidad y con el concepto de legalidad con este relacionado. En este artículo, queremos esbozar un cuadro del cambio del concepto de legalidad con referencia a la evolución de la forma de Estado –de Estado de derecho a Estado social– y al Estado constitucional. La última metamorfosis de la legalidad parece destacar la pérdida o, por lo menos, una crisis profunda de elementos fundamentales –antes que todo, el elemento de la certeza del derecho– que habían caracterizado la estructura y los ideales del concepto tradicional de legalidad., The words expressing essential concepts and fundamental ideas about legal and political theory and practice do not always recur with the same meaning, but they assume a different meaning depending on the different historical and geographical configurations of the civil and political society. The same thing is for the rule of law and for the relative concept of legality. Here, we want to give a hint of how the concept of legality has changed with reference to the evolution of the form of the State, from the legal State to the social State and, finally, to the constitutional State. The last metamorphosis of legality seems to show the loss, or at least, a deep crisis of fundamental elements, first of all the certainty of law, which had marked the structure and the ideals of the traditional concept of legality.

Las palabras que revelan conceptos esenciales y situaciones fundamentales de la teoría y de la práctica jurídica y política no siempre tienen el mismo significado, sino que adquieren significados diferentes con relación a las diversas configuraciones históricas y geográficas de la sociedad civil y de la sociedad política. Lo mismo ocurre con el principio de legalidad y con el concepto de legalidad con este relacionado. En este artículo, queremos esbozar un cuadro del cambio del concepto de legalidad con referencia a la evolución de la forma de Estado –de Estado de derecho a Estado social– y al Estado constitucional. La última metamorfosis de la legalidad parece destacar la pérdida o, por lo menos, una crisis profunda de elementos fundamentales –antes que todo, el elemento de la certeza del derecho– que habían caracterizado la estructura y los ideales del concepto tradicional de legalidad., The words expressing essential concepts and fundamental ideas about legal and political theory and practice do not always recur with the same meaning, but they assume a different meaning depending on the different historical and geographical configurations of the civil and political society. The same thing is for the rule of law and for the relative concept of legality. Here, we want to give a hint of how the concept of legality has changed with reference to the evolution of the form of the State, from the legal State to the social State and, finally, to the constitutional State. The last metamorphosis of legality seems to show the loss, or at least, a deep crisis of fundamental elements, first of all the certainty of law, which had marked the structure and the ideals of the traditional concept of legality.

Sulfuric acid is an important gas influencing atmospheric new particle formation (NPF). Both the binary (H2SO4–H2O) system and the ternary system involving ammonia (H2SO4–H2O–NH3) may be important in the free troposphere. An essential step in the nucleation of aerosol particles from gas-phase precursors is the formation of a dimer, so an understanding of the thermodynamics of dimer formation over a wide range of atmospheric conditions is essential to describe NPF. We have used the CLOUD chamber to conduct nucleation experiments for these systems at temperatures from 208 to 248 K. Neutral monomer and dimer concentrations of sulfuric acid were measured using a chemical ionization mass spectrometer (CIMS). From these measurements, dimer evaporation rates in the binary system were derived for temperatures of 208 and 223 K. We compare these results to literature data from a previous study that was conducted at higher temperatures but is in good agreement with the present study. For the ternary system the formation of H2SO4·NH3 is very likely an essential step in the formation of sulfuric acid dimers, which were measured at 210, 223, and 248 K. We estimate the thermodynamic properties (dH and dS) of the H2SO4·NH3 cluster using a simple heuristic model and the measured data. Furthermore, we report the first measurements of large neutral sulfuric acid clusters containing as many as 10 sulfuric acid molecules for the binary system using chemical ionization–atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometry.

Sulfuric acid is an important gas influencing atmospheric new particle formation (NPF). Both the binary (H2SO4-H2O) system, and the ternary system involving ammonia (H2SO4-H2O-NH3) may be important in the free troposphere. An essential step in the nucleation of aerosol particles from gas-phase precursors is the formation of a dimer, so an understanding of the thermodynamics of dimer formation over a wide range of atmospheric conditions is essential to describe NPF. We have used the CLOUD chamber to conduct nucleation experiments for these systems at temperatures from 208 to 248 K. Neutral monomer and dimer concentrations of sulfuric acid were measured using a Chemical Ionization Mass Spectrometer (CIMS). From these measurements dimer evaporation rates in the binary system were derived for temperatures of 208 and 223 K. We compare these results to literature data from a previous study that was conducted at higher temperatures but is in good agreement with the present study. For the ternary system the formation of H2SO4·NH3 is very likely an essential step in the formation of sulfuric acid dimers, which were measured at 210, 223, and 248K. We estimate the thermodynamic properties (dH and dS) of the H2SO4·NH3 cluster using a simple heuristic model and the measured data. Furthermore, we report the first measurements of large neutral sulfuric acid clusters containing as many as 10 sulfuric acid molecules for the binary system using Chemical Ionization-Atmospheric Pressure interface-Time Of Flight (CI-APi-TOF) mass spectrometry.

Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei(1). Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes(2). Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases(2). However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere(3). It is thought that amines may enhance nucleation(4-16), but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving OUtdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid-amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid-dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation., AuthorCount:79

Highly oxidised organic vapors can effectively stabilize sulphuric acid in heteronuclear clusters and drive new-particle formation. We present quantum chemical calculations of cluster stability, showing that multifunctional species can stabilize sulphuric acid and also present additional polar functional groups for subsequent cluster growth. We also model the multi-generation oxidation of vapors associated with secondary organic aerosol formation using a two-dimensional volatility basis set. The steady-state saturation ratios and absolute concentrations of extremely low volatility products are sufficient to drive new-particle formation with sulphuric acid at atmospherically relevant rates., AuthorCount:11;Funding agencies:U.S. National Science Foundation AGS1136479, CHE1012293; Academy of Finland 1118615, 135054; ERC 257360- MOCAPAF, 27463-ATMNUCLE; Swiss National Science Foundation 200020_135307, 206620_130527; Swedish Research Council, Vetenskapsradet 2011-5120

Growth rates of recently born nanometer-scale particles were measured during the CLOUD experiments at CERN. Combining the data from several recently developed measurement techniques allowed us to follow the growth of the particles starting from molecules to molecular clusters and finally to climatically relevant particles. We studied the binary system with sulphuric acid and water, and the ternary systems with ammonia or dimethylamine added to the chamber, both in purely neutral situation, and with ionization from cosmic rays or the CERN particle beam.

The role of oxidized organic compounds in the process of new particle formation in the atmosphere is poorly known. Here we used the ultraclean and most sophisticated CLOUD chamber to investigate systematically particle formation in the presence of sulfuric acid and oxidized organics. We varied independently the concentrations of both of these components. In addition, nucleation was observed without and in the presence of ionic compounds. From the results a new parameterized description of nucleation was derived for global climate model simulations.

Growth rates of recently born nanometer-scale particles were measured during the CLOUD experiments at CERN. Combining the data from several recently developed measurement techniques allowed us to follow the growth of the particles starting from molecules to molecular clusters and finally to climatically relevant particles. We studied the binary system with sulphuric acid and water, and the ternary systems with ammonia or dimethylamine added to the chamber, both in purely neutral situation, and with ionization from cosmic rays or the CERN particle beam.

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

Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei. Aerosols can cause a net cooling of climate by scattering sunlight and by leading to smaller but more numerous cloud droplets, which makes clouds brighter and extends their lifetimes. Atmospheric aerosols derived from human activities are thought to have compensated for a large fraction of the warming caused by greenhouse gases. However, despite its importance for climate, atmospheric nucleation is poorly understood. Recently, it has been shown that sulphuric acid and ammonia cannot explain particle formation rates observed in the lower atmosphere. It is thought that amines may enhance nucleation, but until now there has been no direct evidence for amine ternary nucleation under atmospheric conditions. Here we use the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN and find that dimethylamine above three parts per trillion by volume can enhance particle formation rates more than 1,000-fold compared with ammonia, sufficient to account for the particle formation rates observed in the atmosphere. Molecular analysis of the clusters reveals that the faster nucleation is explained by a base-stabilization mechanism involving acid–amine pairs, which strongly decrease evaporation. The ion-induced contribution is generally small, reflecting the high stability of sulphuric acid–dimethylamine clusters and indicating that galactic cosmic rays exert only a small influence on their formation, except at low overall formation rates. Our experimental measurements are well reproduced by a dynamical model based on quantum chemical calculations of binding energies of molecular clusters, without any fitted parameters. These results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.

Sulphuric acid, ammonia, amines, and oxidised organics play a crucial role in nanoparticle formation in the atmosphere. In this study, we investigate the composition of nucleated nanoparticles formed from these compounds in the CLOUD (Cosmics Leaving Outdoor Droplets) chamber experiments at CERN (Centre européen pour la recherche nucléaire). The investigation was carried out via analysis of the particle hygroscopicity, ethanol affinity, oxidation state, and ion composition. Hygroscopicity was studied by a hygroscopic tandem differential mobility analyser and a cloud condensation nuclei counter, ethanol affinity by an organic differential mobility analyser and particle oxidation level by a high-resolution time-of-flight aerosol mass spectrometer. The ion composition was studied by an atmospheric pressure interface time-of-flight mass spectrometer. The volume fraction of the organics in the particles during their growth from sizes of a few nanometers to tens of nanometers was derived from measured hygroscopicity assuming the Zdanovskii–Stokes–Robinson relationship, and compared to values gained from the spectrometers. The ZSR-relationship was also applied to obtain the measured ethanol affinities during the particle growth, which were used to derive the volume fractions of sulphuric acid and the other inorganics (e.g. ammonium salts). In the presence of sulphuric acid and ammonia, particles with a mobility diameter of 150 nm were chemically neutralised to ammonium sulphate. In the presence of oxidation products of pinanediol, the organic volume fraction of freshly nucleated particles increased from 0.4 to ~0.9, with an increase in diameter from 2 to 63 nm. Conversely, the sulphuric acid volume fraction decreased from 0.6 to 0.1 when the particle diameter increased from 2 to 50 nm. The results provide information on the composition of nucleated aerosol particles during their growth in the presence of various combinations of sulphuric acid, ammonia, dimethylamine and or

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. The corrections needed to calculate 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. Different test aerosols were generated using a nano-Differential Mobility Analyzer (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 sulphate 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

Sulphuric acid, ammonia, amines, and oxidised organics play a crucial role in nanoparticle formation in the atmosphere. In this study, we investigate the composition of nucleated nanoparticles formed from these compounds in the CLOUD chamber experiments at CERN. The investigation is carried out via analysis of the particle hygroscopicity, ethanol affinity, oxidation state, and ion composition. Hygroscopicity was studied by a hygroscopic tandem differential mobility analyser and a cloud condensation nuclei counter, ethanol affinity by an organic differential mobility analyser and particle oxidation level by a high-resolution time-of-flight aerosol mass spectrometer. The ion composition was studied by an atmospheric pressure interface time-of-flight mass spectrometer. The volume fraction of the organics in the particles during their growth from sizes of a few nanometers to tens of nanometers was derived from measured hygroscopicity assuming the Zdanovski-Stokes-Robinson relationship, and compared to values gained from the spectrometers. The ZSR-relationship was also applied to obtain the measured ethanol affinities during the particle growth, which were used to derive the volume fractions of sulphuric acid and the other inorganics (e.g. ammonium salts). In the presence of sulphuric acid and ammonia, particles with a mobility diameter of 150 nm were chemically neutralised to ammonium sulphate. In the presence of oxidation products of pinanediol, the organic volume fraction of freshly nucleated particles increased from 0.4 to ∼0.9, with an increase in diameter from 2 to 63 nm. Conversely, the sulphuric acid volume fraction decreased from 0.6 to 0.1 when the particle diameter increased from 2 to 50 nm. The results provide information on the composition of nucleated aerosol particles during their growth in the presence of various combinations of sulphuric acid, ammonia, dimethylamine and organic oxidation products.