scholarly journals Drift Velocity and Longitudinal Diffusion Coefficient of Electrons in CO2?Ar Mixtures and Electron Collision Cross Sections for CO2 Molecules

1995 ◽  
Vol 48 (3) ◽  
pp. 357 ◽  
Author(s):  
Y Nakamura
Keyword(s):  
Diffusion Coefficient ◽  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Vibrational Excitation ◽  
Electron Collision ◽  
Longitudinal Diffusion ◽  
Excitation Cross Sections ◽  
Momentum Transfer Cross Section

The drift velocity and longitudinal diffusion coefficient of electrons in 0�2503% and 1� 97% C02-Ar mixtures were measured for 0�03 ~ E/N ~ 20 Td. The measured electron swarm parameters in the mixtures were used to derive a set of consistent vibrational excitation cross sections for the C02 molecule. Analysis of electron swarms in pure C02 using the present vibrational excitation cross sections was also carried out in order to determine a new momentum transfer cross section for the C02 molecule.

scholarly journals The Cross Section for the J = 0 → 2 Rotational Excitation of Hydrogen by Slow Electrons

1969 ◽  
Vol 22 (6) ◽  
pp. 715 ◽  
Author(s):  
RW Crompton ◽  
DK Gibson ◽  
AI McIntosh
Keyword(s):  
Momentum Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Vibrational Excitation ◽  
The Cross ◽  
Excitation Processes ◽  
Slow Electrons ◽  
And Diffusion ◽  
Momentum Transfer Cross Section ◽  
Section Analysis

The results of electron drift and diffusion measurements in parahydrogen have been analysed to determine the cross sections for momentum transfer and for rotational and vibrational excitation. The limited number of possible excitation processes in parahydrogen and the wide separation of the thresholds for these processes make it possible to determine uniquely the J = 0 → 2 rotational cross section from threshold to 0.3 eV. In addition, the momentum transfer cross section has been determined for energies less than 2 eV and it is shown that, near threshold, a vibrational cross section compatible with the data must lie within relatively narrow limits. The problems of uniqueness and accuracy inherent in the swarm method of cross section analysis are discussed. The present results are compared with other recent theoretical and experimental determinations; the agreement with the most recent calculations of Henry and Lane is excellent.

scholarly journals Momentum Transfer Cross Section for Electrons in Mercury Vapour Derived from Drift Velocity Measurements in Mercury Vapour?Gas Mixtures

1991 ◽  
Vol 44 (6) ◽  
pp. 647 ◽  
Author(s):  
JP England ◽  
MT Elford
Keyword(s):  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Personal Communication ◽  
Mercury Vapour ◽  
Semi Empirical ◽  
Time Of Flight Method ◽  
Momentum Transfer Cross Section ◽  
Good Agreement

The Bradbury-Nielsen time-of-flight method has been used to measure electron drift velocities at 573 K in pure mercury vapour, a mixture of 46�80% helium-53� 20% mercury vapour and a mixture of 9�37% nitrogen-90� 63% mercury vapour. The E/N and pressure ranges used were O� 2 to 1� 5 Td and 5�4 to 15�2 kPa for pure mercury vapour, 0 �08 to 3�0 Td and 5 �40 to 26�88kPa for the mixture containing helium and 0�06 to 5�0Td and 3�33 to 16�67kPa for the mixture containing nitrogen. It is shown that the use of mixtures significantly reduces the dependence of the measured drift velocity on the pressure, due to the effect of mercury dimers, from that measured in pure mercury vapour. An iterative procedure to derive the momentum transfer cross section for electrons in mercury vapour over the range 0�04 to 4 eV with an uncertainty between �5 and 10% is described. It is concluded that previously published momentum transfer cross sections for mercury vapour derived from drift velocity data are significantly in error, due to diffusion effects and the procedure used to correct for the influence of dimers. The present cross section is in good agreement with the semi-empirical calculations of Walker (personal communication).

scholarly journals The Ratio DL/ for Electrons in Helium at 293 K

1974 ◽  
Vol 27 (2) ◽  
pp. 235 ◽  
Author(s):  
MT Elford
Keyword(s):  
Diffusion Coefficient ◽  
Momentum Transfer ◽  
Cross Section ◽  
Electron Mobility ◽  
Absolute Error ◽  
Longitudinal Diffusion ◽  
Experimental Errors ◽  
The Common ◽  
The Absolute ◽  
Momentum Transfer Cross Section

The Bradbury–Nielsen method has been used to measure the ratio of the longitudinal diffusion coefficient DL to the electron mobility μ in helium at 293 K over the E/N range 0024–0.607 Td. The absolute error is estimated to be less than � 3 %. The present results agree with those of Wagner et al. (1967), to within the combined experimental errors over the common range of E/N values, and are also compatible with the values predicted by Lowke and Parker (1969) from calculations based on the momentum transfer cross section of Crompton et al. (1967).

scholarly journals Momentum Transfer Cross Section for Electrons in Krypton Derived from Measurements of the Drift Velocity in H2?Kr Mixtures

1988 ◽  
Vol 41 (5) ◽  
pp. 701 ◽  
Author(s):  
JP England ◽  
MT Elford
Keyword(s):  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Personal Communication ◽  
Electron Drift ◽  
Velocity Data ◽  
The Cross ◽  
Momentum Transfer Cross Section ◽  
Made In

Measurements of electron drift velocities have been made in 0�4673% and 1�686% hydrogenkrypton mixtures at 293 K and values of E/ N from 0�08 to 2�5 Td with an estimated uncertainty of <�0�7%. The data have been used in conjunction with the H2 cross sections of England et aL (1988) to derive the momentum transfer cross section for krypton over the energy range 0�05 to 6�0 eV. The drift velocity data have also been used to test the Kr momentum transfer cross sections of Koizumi et aL (1986) and Hunter (personal communication 1988). The cross section of Koizumi et aL is clearly incompatible with the present measurements while the cross section of Hunter has been used to predict these measurements to within 1% to 3%.

scholarly journals The Momentum Transfer Cross Section for Electrons in Mercury Vapour from 0·1 to 5 eV

1980 ◽  
Vol 33 (2) ◽  
pp. 259 ◽  
Author(s):  
MT Elford
Keyword(s):  
Experimental Data ◽  
Energy Range ◽  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Mercury Vapour ◽  
Velocity Data ◽  
Maximum Value ◽  
Momentum Transfer Cross Section

The momentum transfer cross section for electrons in mercury vapour has been derived over the energy range 0�1-5 eV from the drift velocity data of Elford (1980). The cross section has a resonance at 0�5 eV with a maximum value of 180 A 2 (1� 8 x 10-18 m2). It is shown that previous cross sections derived either from experimental data or obtained by ab initio calculations are incompatible with the drift velocity data.

scholarly journals A Swarm Experiment in He–H2 Mixtures to Examine Vibrational Excitation of H2 by Electron Impact

1987 ◽  
Vol 40 (3) ◽  
pp. 347 ◽  
Author(s):  
ZLj Petrovic ◽  
RW Crompton
Keyword(s):  
Momentum Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Vibrational Excitation ◽  
Transport Coefficients ◽  
Pure Hydrogen ◽  
Buffer Gas ◽  
Pure Helium ◽  
Momentum Transfer Cross Section ◽  
Made In

Measurements of electron drift velocities have been made in pure helium and in a helium-hydrogen mixture in order to check the available inelastic cross sections for hydrogen. Although drift velocities in mixtures with helium as the buffer gas are less,sensitive to inelastic scattering by hydrogen than those with argon, the accuracy with which the momentum transfer cross section for helium is known enables the check to be made with virtually no error arising from uncertainty in the momentum transfer cross section for the buffer gas, in contrast to the situation when argon is used. A difference techrtique has been used to minimise the effect of systematic errors in the measurements. The results support the rotational and vibrational cross sections derived from the transport coefficients measured in pure hydrogen.

scholarly journals Momentum Transfer Cross Section for e??Kr Scattering

1993 ◽  
Vol 46 (2) ◽  
pp. 249 ◽  
Author(s):  
MJ Brennan ◽  
KF Ness
Keyword(s):  
Energy Range ◽  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Transport Coefficients ◽  
Velocity Data ◽  
Experimental Errors ◽  
Momentum Transfer Cross Section

The momentum transfer cross section for electrons in krypton has been derived over the energy range Q-4 eV from an analysis of drift velocity and DT/I-' data for hydrogen-krypton mixtures. At energies in the vicinity of the Ramsauer-Townsend minimum, the present work differs significantly from derivations based on analyses of drift velocity data alone. The overall uncertainty in the derived cross section reflects the experimental errors in the transport coefficients, the uncertainty in the cross sections used to represent the hydrogen component in the mixtures, and the uncertainty associated with the X2 minimisation. The present cross section is compared with recent theoretical calculations and other experimental derivations.

scholarly journals The Diffusion Coefficient for Thermal Electrons in Mercury Vapour at 470 K

1980 ◽  
Vol 33 (6) ◽  
pp. 989 ◽  
Author(s):  
R Hegerberg ◽  
RW Crompton
Keyword(s):  
Diffusion Coefficient ◽  
Momentum Transfer ◽  
Cross Section ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Sampling Technique ◽  
Mercury Vapour ◽  
Velocity Data ◽  
Average Momentum ◽  
Momentum Transfer Cross Section

The diffusion coefficient for thermal electrons in mercury vapour has been measured using the CavaIIeri electron density sampling technique. The result indicates that the average momentum transfer cross section for electrons is ~27 x 10−16 cm2, a result which favours previously derived cross sections from drift velocity data over recent theoretical calculations.

scholarly journals A Study of the Vibrational Excitation of H2 by Measurements of the Drift Velocity of Electrons in H2−Ne Mixtures

1988 ◽  
Vol 41 (4) ◽  
pp. 573 ◽  
Author(s):  
JP England ◽  
MT Elford ◽  
RW Crompton
Keyword(s):  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Excitation Cross Section ◽  
Vibrational Excitation ◽  
Pure Hydrogen ◽  
Velocity Data ◽  
Highly Sensitive ◽  
Hydrogen Mixtures ◽  
Made In

Measurements of electron drift velocities have been made in 1�160% and 2�892% hydrogen-neon mixtures at 294 K and values of EI N from 0�12 to 1�7 Td. The measurements are highly sensitive to the region of the threshold of the v = 0 → 1 vibrational excitation cross section for hydrogen and have enabled more definitive tests of proposed cross sections to be made than was possible using drift velocity data for H2−He and H2−Ar mixtures. The theoretical v = 0 → 1 vibrational excitation cross section of Morrison et al. (1987) is shown to be incompatible with the present measurements. A new set of hydrogen cross sections has been derived from the available electron swarm measurements in pure hydrogen and hydrogen mixtures.

scholarly journals Some Recent Studies of Electron Swarms in Gases

1992 ◽  
Vol 45 (3) ◽  
pp. 365 ◽  
Author(s):  
H Tagashira
Keyword(s):  
Boltzmann Equation ◽  
Cross Section ◽  
Electric Fields ◽  
Cross Sections ◽  
Collision Cross Section ◽  
Vibrational Excitation ◽  
Time Spectrum ◽  
Electron Collision ◽  
Electron Drift ◽  
Radio Frequency Electric Fields

Some recent studies of electron swarms in gases under the action of an electric field are introduced. The studies include a new type of continuity equation for electrons having a form in which the partial derivative of the electron density with respect to position and to time are interchanged, a method to deduce the time-of-flight and arrival-time-spectrum swarm parameters based on a Fourier-transformed Boltzmann equation, an examination of the correspondence between experimental and theoretical electron drift velocities, and an automatic technique to deduce the electron-gas molecule collision cross section from electron drift velocity data. We also briefly introduce a method for the deduction of electron collision cross sections with gas molecules having vibrational excitation cross sections greater than the elastic momentum transfer cross section by using a gas mixture technique, an integral type of method for solution of the Boltzmann equation with salient numerical stability, a quantitative analysis of the effect of Penning ionisation, and the behaviour of electron swarms under radio frequency electric fields.

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