178 research outputs found
Inhomogeneous gas model for electron mobility in high density neon gas
Experimental studies of electron mobilities in Neon as a function of the gas
density have persistently shown mobilities up to an order of magnitude smaller
than expected and predicted. A previously ignored mechanism (gas
in--homogeneity which is negligible in the thermal mobilities for He and other
gases) is found to reproduce the observed Neon mobilities accurately and simply
at five temperatures with just one variable parameter. Recognizing that a gas
is not a homogeneous medium, a variation in local density combined with the
quantum multi--scattering theory, shifts the energy and cross section -- which
in turn changes the collision probability and finally the mobilities. A lower
density where a momentum transfer interaction occurs moves the mobility
strongly in the same direction as the anomalous experiments. By going backwards
from the observed mobilities, the collision frequency at each temperature and
density is made to reproduce the experimental data by looking for the local (as
opposed to average) density at which the (rare) momentum transfer interactions
occur. These density deviations give a picture of the size and behavior of the
wave packets for electron motion which looks very much like the often discussed
wave function collapse.Comment: 18 pages, 5 figure
A Carbon Corrosion Model to Evaluate the Effect of Steady State and Transient Operation of a Polymer Electrolyte Membrane Fuel Cell
A carbon corrosion model is developed based on the formation of surface
oxides on carbon and platinum of the polymer electrolyte membrane fuel cell
electrode. The model predicts the rate of carbon corrosion under potential hold
and potential cycling conditions. The model includes the interaction of carbon
surface oxides with transient species like OH radicals to explain observed
carbon corrosion trends under normal PEM fuel cell operating conditions. The
model prediction agrees qualitatively with the experimental data supporting the
hypothesis that the interplay of surface oxide formation on carbon and platinum
is the primary driver of carbon corrosion
Injection of photoelectrons into dense argon gas
The injection of photoelectrons in a gaseous or liquid sample is a widespread
technique to produce a cold plasma in a weakly--ionized system in order to
study the transport properties of electrons in a dense gas or liquid. We report
here the experimental results of photoelectron injection into dense argon gas
at the temperatureT=142.6 K as a function of the externally applied electric
field and gas density. We show that the experimental data can be interpreted in
terms of the so called Young-Bradbury model only if multiple scattering effects
due to the dense environment are taken into account when computing the
scattering properties and the energetics of the electrons.Comment: 18 pages, 10 figures, figure nr. 10 has been redrawn, to be submitted
to Plasma Sources Science and Technolog
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