Uptake of atmospheric molecules by ice nanoparticles: Pickup cross sections

Abstract

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.

Probing RbBr solvation in freestanding sub-2 nm water clusters

“…The value ofC v was calculated similarly. The following heat capacity values for water and He at 100 • C and 1 bar were used 31 With the present experimental conditions, the initial water cluster beam speed (before any pick-up) was calculated to be about 1465 m/s which seems reasonable reflecting on previous measured values 27 .…”

“…Lengyel et al 27 found for water clusters with n = 260 that the pick-up cross-section σ p for all the studied dopant molecules is always larger than the geometric cross-section σ g = πr 2 n , where r n is the cluster radius. Measurements indicated for example for the pickup of water molecules on water cluster σ p /σ g = 2.5 and for HBr, σ p /σ g = 1.4.…”

“…Measurements indicated for example for the pickup of water molecules on water cluster σ p /σ g = 2.5 and for HBr, σ p /σ g = 1.4. In general, the pick-up cross section depends on the interaction potential between the cluster and the molecule, the mass of the molecule and the relative velocity between the two 27 .…”

The temperature and size distribution of large water clusters from a non-equilibrium model

“…The values of the water cluster heat capacities as a function of the cluster size are given in Table I Another possible source of error in numerical modeling are the cluster cross sections used for cluster-monomer and cluster-cluster collisions. 30,31 We used an empirical expression for the diameter d of water clusters,…”

Extensive water cluster fragmentation after low energy electron ionization

“…Large (H 2 O) N clusters withN ≈ 10-10 3 represent laboratory model to mimic 5 important systems and processes, e.g., cloud particle and aerosol nucleation [4,5,6,7,8], chemistry and photochemistry on ice particles in atmosphere [9,10,11,12], processes in radiation chemistry [13], processes in chemistry and biology induced and controlled by solvent [14] etc. In many laboratory studies water clusters are detected by mass spectrometric methods.…”