scholarly journals Electron Drift and Diffusion in Parahydrogen at 77°K

1968 ◽  
Vol 21 (5) ◽  
pp. 637 ◽  
Author(s):  
RW Crompton ◽  
AI McIntosh
Keyword(s):  
Diffusion Coefficient ◽  
Energy Distribution ◽  
Vibrational Excitation ◽  
Electron Drift ◽  
Thermal Region ◽  
Dominant Process ◽  
Series Of Experiments ◽  
Normal Hydrogen ◽  
The Difference ◽  
And Diffusion

This paper reports a series of experiments to measure electron diffusion and drift in pure parahydrogen at 77° K. Tables of data are given for the electron drift velocity W in the range 1.2 X l0−19 ≤ E/N ≤ 9.5 x l0−17 V cm2 and for the ratio of diffusion coefficient to mobility D/μ for 2 X 10−20 ≤ E/N ≤ 6 X 10−17 V cm2. As expected, these data are indistinguishable from the data for normal hydrogen in the thermal region and at the higher values of E/N where vibrational excitation is the dominant process controlling the electron energy distribution. However, at intermediate values of E/N, the values of W and D/μ differ by more than 10 and 20% respectively from the corresponding values in normal hydrogen, demonstrating the influence of the difference in the statistical weights of the rotational levels in the two gases.

scholarly journals Electron Drift And Diffusion In Deuterium At 293°K

1966 ◽  
Vol 19 (6) ◽  
pp. 805 ◽  
Keyword(s):  
Diffusion Coefficient ◽  
Drift Velocity ◽  
Electron Drift ◽  
And Diffusion

The drift velocity and the ratio of diffusion coefficient to mobility have been measured for electrons in deuterium at 293�K over the ranges 0�006 � E/p � 5�0 and 0�006 � E/p � 2�0 respectively. The results are compared with those of other workers.

A Model Study on the Diffusion and the Dilution of Low Molecular Weight Gaseous Components through Cigarette Paper during Smoking

1977 ◽  
Vol 9 (3) ◽  
Author(s):  
M. Muramatsu ◽  
T. Mikami ◽  
N. Naito ◽  
H. Tomita
Keyword(s):  
Diffusion Coefficient ◽  
Gas Mixture ◽  
Low Molecular Weight ◽  
Diffusion Loss ◽  
Front End ◽  
Model Study ◽  
The Difference ◽  
Cigarette Paper ◽  
And Diffusion ◽  
Standard Gas

AbstractThe effects of diffusion and dilution on the concentration of gaseous components have been studied by a model consisting of unlit cigarettes differing in paper porosity and length, and a standard gas mixture. Results are as follows: The difference in the concentration of gaseous components between the front and butt end of the cigarette during the puff increases with cigarette length and paper porosity, and also depends on the diffusion coefficient of respective components through the cigarette paper. These changes could be explained mainly by the diffusion loss through the paper in the case of the cigarette with ordinary paper, but by both dilution with air through the paper and diffusion loss in the case of the cigarette with perforated paper. Subsequently, the levels of gaseous components such as carbon monoxide in the exit stream become lower in the Iatter cigarette. In addition, the following equation, which can fully account for these changes, has been derived:where C1i and C0i are the concentrations of the component i at the front and butt end, respectively, L the cigarette length, r the cigarette radius, s the thickness of paper, U0 and U1 the apparent linear gas velocities at the butt and front end, respectively, and Di the diffusion coefficient of component i through the paper.

scholarly journals Computer Simulation of an Electron Swarm at low E/p in Helium

1974 ◽  
Vol 27 (1) ◽  
pp. 59 ◽  
Author(s):  
AI McIntosh
Keyword(s):  
Computer Simulation ◽  
Diffusion Coefficient ◽  
Cross Section ◽  
Electron Energy Distribution Function ◽  
Recent Theory ◽  
Electron Drift ◽  
Longitudinal Diffusion ◽  
Transverse Diffusion ◽  
And Diffusion ◽  
Momentum Transfer Cross Section

A computer simulated electron swarm at E/P293 = 1�0 V cm -1 tore 1 in a model gas has been used to examine the validity of a recent theory of electron drift and diffusion. The computed results are in agreement with well-established theories for the electron energy distribution function, drift velocity and transverse diffusion coefficient, and confirm that, for a constant momentum transfer cross section, the longitudinal diffusion coefficient is approximately half the transverse coefficient. However, significant differences have been found between the computed swarm and the predictions of the theory of Huxley (1972). In particular, over the time scale considered, the electron swarm is not symmetric about its centroid but is spatially anisotropic in such a way that it could appropriately be described as 'pear shaped'.

Solvent diffusion in porous low-k dielectric films

2003 ◽  
Vol 766 ◽  
Author(s):  
Denis Shamiryan ◽  
Karen Maex
Keyword(s):  
Dielectric Constant ◽  
Diffusion Coefficient ◽  
Porous Matrix ◽  
Silicon Oxycarbide ◽  
Dielectric Films ◽  
Polar Solvents ◽  
Low Dielectric ◽  
The Difference ◽  
Low K ◽  
And Diffusion

AbstractPorous materials are being investigated as low dielectric constant (low-k) materials. While porosity decreases the k-value of a material by decreasing its density, it simultaneously allows unwanted adsorption and diffusion of chemicals inside the porous matrix. To investigate this, different porous low-k materials, specifically silicon oxycarbide (SiOCH), methylsilsesquioxane (MSQ), and a polymer, were exposed to polar (ethanol) and non-polar (toluene) solvents. A difference in diffusion of polar and non-polar solvents would be an indication of the density of polar centers which attract polar molecules (such as water) and increase the dielectric constant of a film. The diffusion coefficient for toluene at room temperature was found to be approximately 2×10-5 cm2/sec for MSQ (40% porosity), 10-7 cm2/sec for SiOCH (7% porosity), 2×10-8 cm2/sec for the polymer. The observed diffusion can be described by a model of a viscous flow in a porous medium. The toluene/ethanol diffusion coefficient ratios were 4.4, 1.3, 1 for MSQ, SiOCH, and the polymer, respectively. The difference in toluene/ethanol diffusion can potentially be used to screen a material's affinity for water adsorption.

Calculation Method about Vertical Distribution of Saturated Sediment Concentration Based on Exchange Equilibrium

2013 ◽  
Vol 405-408 ◽  
pp. 2287-2291
Author(s):  
Xiao Xiang Feng ◽  
Pei Jiu Yue
Keyword(s):  
Diffusion Coefficient ◽  
Vertical Distribution ◽  
Diffusion Theory ◽  
Sediment Concentration ◽  
Exchange Equilibrium ◽  
Sediment Diffusion Coefficient ◽  
The Difference ◽  
The Vertical Distribution ◽  
And Diffusion ◽  
Key Parameter

Diffusion theory is the leading one which is used to study the vertical distribution of sediment concentration. And diffusion coefficient is a key parameter to determine the vertical distribution of suspended sediment. First of all, the calculation methods are introduced based on the momentum transfer theory and fluctuating velocity. According to the sediment equation of exchange equilibrium in vertical, the new expression is obtained for sediment diffusion coefficient and the vertical distribution of sediment concentration. By the flume experimental data and field data in natural river, the difference is analyzed among the different expressions.

PERMEABILITY AND DIFFUSION COEFFICIENT PREDICTION OF FRACTAL POROUS MEDIA WITH NANOSCALE PORES FOR GAS TRANSPORT

2018 ◽  
Vol 21 (12) ◽  
pp. 1253-1263
Author(s):  
Ruifei Wang ◽  
Hongqing Song ◽  
Jiulong Wang ◽  
Yuhe Wang
Keyword(s):  
Porous Media ◽  
Diffusion Coefficient ◽  
Gas Transport ◽  
And Diffusion

Diffusion of Zn into Gaas 0.6 P0.4:Te From Zn-Doped Oxide Films By Rapid Thermal Processing

1987 ◽  
Vol 92 ◽  
Author(s):  
A. Usami ◽  
Y. Tokuda ◽  
H. Shiraki ◽  
H. Ueda ◽  
T. Wada ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Thermal Processing ◽  
Rapid Thermal Processing ◽  
Oxide Films ◽  
Zn Diffusion ◽  
Enhanced Diffusion ◽  
Conventional Furnace ◽  
Zn Concentration ◽  
The Difference ◽  
Doped Oxide

ABSTRACTRapid thermal processing using halogen lamps was applied to the diffusion of Zn into GaAs0.6 P0.4:Te from Zn-doped oxide films. The Zn diffusion coefficient of the rapid thermal diffused (RTD) samples at 800°C for 6 s was about two orders of magnitude higher than that of the conventional furnace diffused samples at 800°C for 60 min. The enhanced diffusion of Zn by RTD may be ascribed to the stress field due to the difference in the thermal expansion coefficient between the doped oxide films and GaAs0.6P0.4 materials, and due to the temperature gradient in GaAs0.6P0 4 materials. The Zn diffusion coefficient at Zn concentration of 1.0 × l018 cm−3 was 3.6 × 10−11, 3.1 × 10−11 and 5.0 × 10−12 cm2 /s for the RTD samples at 950°C for 6 s from Zn-, (Zn,Ga)- and (Zn,P)-doped oxide films, respectively. This suggests that Zn diffusibility was controlled by the P in the doped oxide films.

Diffusion Constant and Diffusion Coefficient

Science ◽  
1955 ◽  
Vol 121 (3137) ◽  
pp. 215-216 ◽  
Author(s):  
J. VERDUIN
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Constant ◽  
And Diffusion
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