scholarly journals Zero-field Mobility for Electrons in Dry and Humid Air

1975 ◽  
Vol 28 (2) ◽  
pp. 231 ◽  
Author(s):  
HB Milloy ◽  
ID Reid ◽  
RW Crompton
Keyword(s):  
Relative Humidity ◽  
Momentum Transfer ◽  
Water Vapour ◽  
Cross Section ◽  
Drift Tube ◽  
Zero Field ◽  
Humid Air ◽  
Dry Air ◽  
Field Mobility ◽  
Momentum Transfer Cross Section

The zero-field mobility of electrons in dry and humid air at 294 K has been studied with drift tube techniques. For air containing 1.5 % water vapour (50 % relative humidity) the zero-field mobility was found to be 8.4 � 0.2 X 105 cm s−l Td−l. The zero-field mobility of electrons in dry air (4.7 � 0.2 x 106 cm s−l Td−l) was deduced from measurements in which small quantities of CO2 Were added to reduce the electron energy. It is estimated that the momentum transfer cross section for electron–oxygen collisions, at near thermal energies, is at least four times smaller than it is for electron–nitrogen collisions.

The Drift Velocity of Electrons in Water Vapour at Low Values of E/N

1990 ◽  
Vol 43 (6) ◽  
pp. 755 ◽  
Keyword(s):  
Momentum Transfer ◽  
Water Vapour ◽  
Cross Section ◽  
Drift Velocity ◽  
Velocity Measurements ◽  
Low Energies ◽  
Momentum Transfer Cross Section

The drift velocity of electrons in water vapour at 294 K has been measured over the E/N range 1�4 to 40 Td with an error estimated to be 35 Td. The present data show that J.lN decreases monotonically with decreasing E/N at low E/N values as observed by Wilson et al. (1975) and does not become independent of E/N as indicated by Lowke and Rees (1963). The present values, although lower than those of Lowke and Rees, lie within the combined error limits, except for values below 2 Td. The present data suggest that the momentum transfer cross section at low energies is approximately 10% larger than that obtained by Pack et al. (1962) from their drift velocity measurements.

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 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 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).

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