Sign Of Charge Transfer Research Articles

A modelling study of the effect of ice particle sizes and relative velocity on ice crystal/graupel collisional charge transfer

The effect of ice particle sizes and relative velocity on the sign of charge transfer during graupel/ice crystal interactions in thunderstorms is considered based on the concept of the Relative Growth Rate Hypothesis that the ice surface growing faster by water vapour diffusion charges positively. Diffusional growth rates of ice crystals and riming graupel particles are calculated for various particle sizes and velocities, and the sign of charging during crystal/graupel collisions is determined. The study reveals that larger graupel charges more negatively, while larger ice crystals, or higher relative velocity, lead to increased positive graupel charging.

A laboratory study of the influence of ice crystal growth conditions on subsequent charge transfer in thunderstorm electrification

AbstractLaboratory studies of a thunderstorm charging mechanism involving rebounding collisions between ice crystals and riming graupel pellets, have shown the importance of the growth conditions of the interacting ice particles on the sign of the charge transferred. The present study shows a new result: if an ice crystal is not in thermal equilibrium with the environment (immediately following the mixing of two clouds at different saturations) the crystal surface may experience an enhanced growth rate that can influence the sign of the charge transfer and promote negative rimer charging. Furthermore, when an ice crystal in ice saturation conditions is introduced to a cloud at water saturation, leading to transient growth and heating, the period of thermal non‐equilibrium is shown to be sufficiently brief that the enhanced negative rimer charging is short lived. These results suggest that the earlier conclusions of Berdeklis and List—that the cloud saturation conditions around a growing ice crystal impart to the crystal surface a property that is carried with it and that influences the sign of subsequent charge transfer—are unfounded. The discrepancy is because in their laboratory simulations of thunderstorm conditions there is adequate time for the growing ice crystal surface to come to equilibrium with its environment. The established concept of the relative diffusional growth rate of the interacting surfaces controlling the sign of charge transfer, such that the faster growing surface charges positively, is consistent with the observations. Copyright © 2004 Royal Meteorological Society

Synthesis of PtN x films by reactive laser ablation

Thin films of platinum containing up to ∼14 at.% nitrogen have been prepared by reactive laser ablation in molecular nitrogen ambient. The films are characterized in situ by Auger, X-ray photoelectron and electron energy loss spectroscopies (AES, XPS and EELS, respectively). The N 1s binding energy of 398.4 eV supports the existence of chemisorbed nitrogen. Moreover, a +0.2 eV shift of the Pt 4f peak position is a sign of charge transfer from Pt to N. In addition, alterations in the loss characteristics are indicating changes in the electronic configuration. It is concluded that platinum is forming an incipient nitride phase with composition near to Pt 6N.

The relation between contact charge transfer and chemical donor properties

The physical concept of a triboelectric series of materials and the chemical concept of the relative electron donor strengths of molecules both refer to a tendency to transfer electrons. In this work, contact charge transfer has been observed, using a variety of liquids and solids. It is shown that the sign of charge transfer is related to the chemical donicity of liquids as determined from thermodynamic data.