Capture of vapor molecules by a realistic attraction potential of a drop

Васильев, О.В.; Reiss, Howard

doi:10.1063/1.472161

Cited by 22 publications

(9 citation statements)

References 2 publications

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“…This can be explained by a large increase of the cross section for capture of molecules from the vapor due to the diffuse nature of the outer layer of the cluster and also as a result of its attractive potential. [39][40][41] This result re- emphasizes the fact that one should not expect an n 2/3 law for the ␥'s, but rather a linear increase of magnitude with n.…”

Section: Multimolecule Events Involve Clusters Evaluation Ofmentioning

confidence: 66%

Simulative determination of kinetic coefficients for nucleation rates

Schaaf

Senger

Voegel

et al. 2001

The Journal of Chemical Physics

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A unimolecular evaporation model for simulating argon condensation flows in direct simulation Monte Carlo Phys. Fluids 21, 036101 (2009); 10.1063/1.3094957 Evaluating nucleation rates in direct simulationsNucleation kinetics can be formulated generally and rigorously as a set of master equations that govern the time evolution of the cluster distribution that underlies the observable rate process. However, this general formulation is only useful if the magnitudes of the coefficients that describe the loss and gain ͑evaporation and condensation͒ of molecules by a cluster are quantitatively known. Moreover, these coefficients can refer to multiple losses and gains of molecules ͑several molecules in a single step͒. In order to measure these coefficients accurately and efficiently, we have devised a molecular dynamics ͑MD͒ simulation that follows the development and equilibration of a single cluster in a small container ͑volume͒ that involves only a small number of molecules ͑in our case 216͒. There is evidence that such a system can provide a reliable picture of the behavior of a cluster in a larger system. This approach has been applied to supersaturated argon vapor at 85 K. In particular, we have been able to study the fluctuation in the size of the ''equilibrium'' cluster that develops in the small volume and, from these observations, to determine the evaporation and condensation coefficients. Besides yielding the values of these coefficients, the study has allowed us to establish several points, including the validity of detailed balance within the simulation, the importance of multimolecular losses and gains of molecules, and the intrinsic nature ͑nonimportance of the surrounding vapor͒ of the evaporation coefficients. Also, it is shown that the clusters disappear by a first order decay law, thus establishing the relevance of the linear form of the set of master equations that can be used to describe the nucleation process. It is also established, by our first estimates of the condensation coefficients, that they are an order of magnitude larger than those predicted by the simple molecular kinetic theory used in classical nucleation theory ͑CNT͒, suggesting the effects of the diffuse outer layers of the actual physical cluster and the role of the cluster's attractive potential. In addition, we have performed an analysis, involving the statistics of correlation, that strongly supports the idea that multimolecule losses and gains experienced by a cluster are chiefly due to the departure and arrival of smaller ''clusters.'' Finally, we have modeled the nucleation process in the small system, using CNT, and have found that in many respects CNT provides a good account of the phenomena observed by means of MD. Because of the ''intrinsic nature'' of the evaporation coefficient, it is possible to perform the simulations at quite high levels of supersaturation, thereby accelerating the approach to equilibrium, and requiring less computer capacity. The evaporation coefficient of the ''equilibrium cluster'' that forms the ...

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Section: Multimolecule Events Involve Clusters Evaluation Ofmentioning

confidence: 66%

Simulative determination of kinetic coefficients for nucleation rates

Schaaf

Senger

Voegel

et al. 2001

The Journal of Chemical Physics

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“…within a factor of 2) for

\frac{z e μ_{D}}{4 π ϵ_{0} k T {(() r_{g} + r_{v})}^{2}}

<4, which is true for all ion‐vapor molecule complexes containing more than two vapor molecules in the present study. For larger values of

\frac{z e μ_{D}}{4 π ϵ_{0} k T {(() r_{g} + r_{v})}^{2}}

, the equation of Nadytko and Yu implies that the collision rate between vapor molecules and an ion increases with decreasing ion size, which is physically unreasonable, and predicts rates in excess of the C 1 =1 in Equation (4c), which is the fully aligned dipole collision rate derived via the approach of Vasil'ev and Reiss . We therefore utilize Equation (4c) in all calculations presented here.…”

Section: Resultsmentioning

confidence: 99%

Examination of Organic Vapor Adsorption onto Alkali Metal and Halide Atomic Ions by using Ion Mobility Mass Spectrometry

Maiβer

Hogan

2017

ChemPhysChem

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We utilize ion mobility mass spectrometry with an atmospheric pressure differential mobility analyzer coupled to a time‐of‐flight mass spectrometer (DMA‐MS) to examine the formation of ion‐vapor molecule complexes with seed ions of K+, Rb+, Cs+, Br−, and I− exposed to n‐butanol and n‐nonane vapor under subsaturated conditions. Ion‐vapor molecule complex formation is indicated by a shift in the apparent mobility of each ion. Measurement results are compared to predicted mobility shifts based upon the Kelvin–Thomson equation, which is commonly used in predicting rates of ion‐induced nucleation. We find that n‐butanol at saturation ratios as low as 0.03 readily binds to all seed ions, leading to mobility shifts in excess of 35 %. Conversely, the binding of n‐nonane is not detectable for any ion for saturation ratios in the 0–0.27 range. An inverse correlation between the ionic radius of the initial seed and the extent of n‐butanol uptake is observed, such that at elevated n‐butanol concentrations, the smallest ion (K+) has the smallest apparent mobility and the largest (I−) has the largest apparent mobility. Though the differences in behavior of the two vapor molecules types examined and the observed effect of ionic seed radius are not accounted for by the Kelvin–Thomson equation, its predictions are in good agreement with measured mobility shifts for Rb+, Cs+, and Br− in the presence of n‐butanol (typically within 10 % of measurements).

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“…The question arises, whether the actual pickup cross section will follow the size dependence of the geometrical cross section. The effect of long-range forces in the cluster-molecule collision has been theoretically investigated by Vasilev and Reiss, 27,28 for water droplets and by Vigué et al 29 for argon clusters. The later work has shown that the capture cross section for Ar N clusters (which is also larger than the geometrical cross section) scales as N 2/3 for N 10 3 .…”

Section: Discussionmentioning

confidence: 99%

Uptake of atmospheric molecules by ice nanoparticles: Pickup cross sections

Lengyel

Kočišek

Poterya

et al. 2012

The Journal of Chemical Physics

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Uptake of several atmospheric molecules on free ice nanoparticles was investigated. Typical examples were chosen: water, methane, NO x species (NO, NO 2 ), hydrogen halides (HCl, HBr), and volatile organic compounds (CH 3 OH, CH 3 CH 2 OH). The cross sections for pickup of these molecules on ice nanoparticles (H 2 O) N with the mean size ofN ≈ 260 (diameter ∼2.3 nm) were measured in a molecular beam experiment. These cross sections were determined from the cluster beam velocity decrease due to the momentum transfer during the pickup process. For water molecules molecular dynamics simulations were performed to learn the details of the pickup process. The experimental results for water are in good agreement with the simulations. The pickup cross sections of ice particles of several nanometers in diameter can be more than 3 times larger than the geometrical cross sections of these particles. This can have significant consequences in modelling of atmospheric ice nanoparticles, e.g., their growth.

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Capture of vapor molecules by a realistic attraction potential of a drop

Abstract: We derive the rate of the capture of a molecule from the surrounding dilute vapor by a drop with a realistic attraction potential. For a small drop, which is of interest in the vapor phase nucleation theory, the result is substantially different from the conventional one.

Cited by 22 publications

References 2 publications

Simulative determination of kinetic coefficients for nucleation rates

Simulative determination of kinetic coefficients for nucleation rates

Examination of Organic Vapor Adsorption onto Alkali Metal and Halide Atomic Ions by using Ion Mobility Mass Spectrometry

Uptake of atmospheric molecules by ice nanoparticles: Pickup cross sections

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