Surface vibrations of large water clusters by helium atom scattering

Brudermann, Jesko; Lohbrandt, Petra; Buck, U.; Buch, V.

doi:10.1063/1.481744

Cited by 21 publications

(16 citation statements)

References 34 publications

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“…The most significant parameter in relation (4) is the vibrational time  v associated to the period of the main surface vibrational mode of the cluster excited in the collision 3,4 ). The characteristic time  v (0.66 ps) deduced from our experiments on water is close to the period of the main low-energy surface vibrational mode excited by collisions of rare gas atoms onto water clusters, the O· ·O· ·O bending mode 16,17 .…”

Section: ) Attachment Of Water Molecules Onto Water Clusterssupporting

confidence: 66%

Attachment of Water and Alcohol Molecules onto Water and Alcohol Clusters

et al. 2015

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Absolute attachment cross sections of single molecules M (M = water, ethanol, or methanol) onto positively charged mass-selected clusters XnH(+) (X = water, ethanol, or methanol) were measured for cluster sizes ranging from tens to hundreds of molecules and center-of-mass collision energies varying from 0.1 to ∼1 eV. The attachment cross sections, which converge as expected toward geometrical cross sections at large cluster sizes, are systematically and noticeably lower than geometrical cross sections at small sizes. Attachment cross sections depend barely on the nature of the reactants. Homogeneous attachment reactions XnH(+) + X → Xn+1H(+) can be accounted for by a dynamical collisional model, in which the intermolecular interactions between the target cluster and the impinging molecule can be neglected. Dynamical arguments account satisfactorily for size and energy dependences of attachment cross sections and also for their variation from one element to another. It is thus suggested that either the attachment probabilities are likely to be more governed by the capacity of clusters to absorb collision energy rather than by cluster/molecule intermolecular interactions, or it indicates that the strength of these interactions does not differ noticeably among the hydrogen-bonded systems investigated. However, for inhomogeneous reactions of the form XnH(+) + Y → XnYH(+) (X, Y = water, ethanol, methanol), although the global size dependences are qualitatively reproduced, the variations of attachment cross sections with the nature on the impinging molecule are not satisfactorily accounted for within the simple empirical model proposed for homogeneous reactions.

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Section: ) Attachment Of Water Molecules Onto Water Clusterssupporting

confidence: 66%

Attachment of Water and Alcohol Molecules onto Water and Alcohol Clusters

et al. 2015

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“…The cluster temperature was assumed to be 90 K-this was chosen as a compromise between 70 and 100 K as estimated in Ref. 26 for a cluster source identical to ours. Then the cluster was randomly rotated and the H 2 O projectile was shot at the cluster with a certain impact parameter and velocity of 1450 ms −1 , equal to velocity of cluster beam in the experiment.…”

Section: Theoretical Cross Sections For Water Pickupmentioning

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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“…We estimated initially the temperature of our ammonia clusters T c ϭ50 K from the value obtained recently from the deexcitation of water clusters in collisions with helium. 6 We found T c ϭ69-101 K in the size range ͗n͘ϭ80-194. Since the binding energy is somewhat smaller for ammonia, the lower value T c ϭ50 K was specified.…”

Section: Vibrational Excitationmentioning

confidence: 62%

“…This result is quite similar to that observed for water clusters in this size range where only the bending motion of the O atoms is excited. 6 With increasing deflection angle, the energy transfer is completely dominated by multiphonon excitations up to the point where no intensity is left at the position of the single-phonon excitation.…”

Section: Vibrational Excitationmentioning

confidence: 99%

“…In the case of water, accompanying calculations demonstrated that at 5.5 meV mainly the O-O-O bending motion of three-coordinated surface molecules was excited. 6 For ammonia clusters which exhibit larger energy transfers in the range from 6 to 60 meV no calculations were available. We note that the collision energy for the molecular clusters was with 57/72 meV for water and 91/100 meV for ammonia clusters, much larger than the 25 meV used in the argon cluster experiment.…”

Section: Introductionmentioning

confidence: 99%

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Intermolecular vibrations of large ammonia clusters from helium atom scattering

Beu¹,

Steinbach²,

Buck³

2002

The Journal of Chemical Physics

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The excitation of the low-energy intermolecular modes of ammonia clusters by helium atom scattering has been calculated using classical trajectories. The energy transfer is investigated as a function of scattering angle ͑from 10°to 90°͒, collision energy ͑94.8 and 50.5 meV͒, cluster size (nϭ18, 100, 1000͒, and cluster temperature (T c ϭ1 K, 30-50 K, and 105 K͒. It is observed that predominantly the mode at 7 meV and to a lesser extent also the one at 12 meV are excited. These are surface modes that mainly originate from the angular motion of three adjacent N atoms. The excitation is nearly independent of the cluster size and the probability for multiphonon excitation steadily increases with increasing deflection angle. This trend is even strengthened by increasing the collision energy. The role of the cluster temperature is to broaden the energy transfer distribution with increasing values. The calculations are compared with previous and new measurements presented here of the double-differential cross sections (d/d) ⌬E of ammonia clusters of average size ͗n͘ϭ92 at two collision energies and ͗n͘ϭ1040 at one energy. While the general trends in the angular and energy dependence could be well reproduced, the correct cluster temperature was crucial in getting good agreement at the lower collision energy for nϭ100. At the higher collision energy, the large energy transfer is not reproduced, probably a shortcoming of the potential models to account correctly for the anharmonicity of the strong multiquantum excitations.

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Surface vibrations of large water clusters by helium atom scattering

Cited by 21 publications

References 34 publications

Attachment of Water and Alcohol Molecules onto Water and Alcohol Clusters

Attachment of Water and Alcohol Molecules onto Water and Alcohol Clusters

Uptake of atmospheric molecules by ice nanoparticles: Pickup cross sections

Intermolecular vibrations of large ammonia clusters from helium atom scattering

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