scholarly journals The Diffusion of Slow Electrons in Deuterium

1955 ◽  
Vol 8 (4) ◽  
pp. 468 ◽  
Author(s):  
Barbara IH Hall
Keyword(s):  
Cross Section ◽  
Mean Free Path ◽  
Lateral Spread ◽  
Electron Stream ◽  
Collisional Cross Section ◽  
The Mean ◽  
Energy Coefficient ◽  
Slow Electrons ◽  
Deuterium Molecule ◽  
Unit Pressure

The agitational energies and drift velocities of slow electrons diffusing in deuterium are measured as a function of the ratio Z/p of the electric field strength Z to the gas pressure p. The lateral spread of the diffusing electron stream is measured, which enables Townsend's energy coefficient to be calculated. Drift velocities are measured using a magnetic deflection method. On the basis of the kinetic theory of gases these measurements are used to calculate values for the mean free path L of the electrons at unit pressure, the mean proportion η of the energy lost by an electron in a collision with a deuterium molecule, and the collisional cross section A of the molecules in collisions with the electrons. The values obtained are compared with those of Crompton and Sutton (1952) for hydrogen.

scholarly journals Experimental and theoretical studies of the behaviour of slow electrons in air. I

1949 ◽  
Vol 196 (1046) ◽  
pp. 402-426 ◽  
Keyword(s):  
Drift Velocity ◽  
Mean Free Path ◽  
Free Electrons ◽  
Direct Measurements ◽  
Electronic Motion ◽  
The Mean ◽  
Gas Molecules ◽  
Slow Electrons ◽  
Experimental And Theoretical Studies ◽  
Unit Pressure

This paper is an account of an experimental investigation of the motions of free electrons in air by the method developed by Townsend. An improved form of apparatus is described with the appropriate theory. The following parameters of the electronic motion were determined as functions of the ratio Z/p of the electric field strength Z to the gas pressure p : Townsend’s energy factor k r the drift velocity W , the mean free path at unit pressure L and the mean proportion n of its energy lost in collisions with gas molecules. The experimental data are given in the form of tables and curves. The drift velocity W is found by a new procedure based on the Hall effect and by comparing the velocities W so obtained with the direct measurements of W by Nielsen & Bradbury it is seen that the velocities of agitation are distributed approximately according to Druyvesteyn’s law when Z/p exceeds 0.5. Bailey’s factor G , which is of importance in ionospheric studies, is obtained from the experimental dependence of η on k r . Theoretical formulae are derived for k r and W in terms of L, G and Z/p . The theory of the new method for measuring W is given in an appendix.

Experimental investigation of the diffusion of slow electrons in nitrogen and hydrogen

1952 ◽  
Vol 215 (1123) ◽  
pp. 467-480 ◽  
Keyword(s):  
Experimental Investigation ◽  
Cross Sections ◽  
Mean Free Path ◽  
Uniform Electric Field ◽  
Tabular Form ◽  
Energy Coefficient ◽  
Slow Electrons ◽  
Physical Quantities ◽  
Unit Pressure ◽  
Gas Pressures

This paper presents the results of precise measurements of the diffusion of slow electrons in hydrogen and nitrogen in the presence of a uniform electric field. Such measurements lead directly to the value of Townsend’s energy coefficient ( k T ) as a function of Z/p (field strength/gas pressure). Since the drift velocity ( W ) of the electrons is also known (Nielsen & Bradbury 1936), the following physical quantities are deduced as functions of Z/p : mean free path of the electrons at unit pressure, mean energy lost by an electron per collision and the collisional cross-sections of the molecules. Measurements of the diffusion were obtained from two apparatuses which differed in dimensions and metal of the electrodes. The range of gas pressures employed was 3 to 14 mm of mercury. A table shows that the values of k T as a function of Z/p derived from these measurements agree (with one exception) to within 3%, and it is therefore considered that the measurements are trustworthy. The results are presented graphically and in tabular form.

scholarly journals Applications Aspects of the Diffusion of Slow Electrons in the Ionospheric Gases

2012 ◽  
Vol 9 (2) ◽  
pp. 341-351
Author(s):  
Baghdad Science Journal
Keyword(s):  
Electric Field ◽  
Collision Frequency ◽  
Mean Free Path ◽  
Uniform Electric Field ◽  
Mean Velocity ◽  
Pure Nitrogen ◽  
Characteristic Energy ◽  
Exchange Collision ◽  
Collisional Cross Section ◽  
Slow Electrons

The paper presents the results of precise of the calculations of the diffusion of slow electrons in ionospheric gases, such as, (Argon – Hydrogen mixture, pure Nitrogen and Argon – Helium – Nitrogen) in the presence of a uniform electric field and temperature 300 Kelvin. Such calculations lead to the value Townsend's energy coefficient (KT) as a function of E/P (electric field strength/gas pressure), electric field (E), electric drift velocity (Vd), momentum transfer collision frequency ( ), energy exchange collision frequency ( ) and characteristic energy (D/?). The following physical quantities are deduced as function s E/P: mean free path of the electrons at unit pressure, mean energy lost by an electron per collision, mean velocity of agitation and the collisional cross-section of the molecules. The results are presented graphically and in tabular form. This results appeared a good agreement with the experimental data.

DETERMINATION OF THE MEAN FREE PATH OF SLOW ELECTRONS BY THE MEASUREMENT OF BACK-DIFFUSION IN HELIUM AND ARGON

1965 ◽  
Vol 43 (3) ◽  
pp. 422-431 ◽  
Author(s):  
O. J. Orient
Keyword(s):  
Energy Distribution ◽  
Free Path ◽  
Electron Energy ◽  
Field Intensity ◽  
Mean Free Path ◽  
Back Diffusion ◽  
Test Device ◽  
The Mean ◽  
Slow Electrons

In the theoretical examination of back-diffusion Varney found a relationship between the extent of the back-diffusion of electrons starting from the cathode and the distance to the cathode. When adequate conditions are ensured the dependence of back-diffusion on distance permits the determination of the mean free path of the electrons. A test device has been developed to measure back-diffusion as a function of the distance to the cathode, for electrons that have an energy distribution corresponding to the specified pressure and the field intensity. From the dependence on distance, mean free paths for helium and argon gases in the range from X/p = 0.5 volt/cm. mm Hg to X/p = 5 volts/cm. mm Hg have been determined. The results are in fair accordance with the mean free paths computed by Barbiere from electron-energy distribution values. Variances have been found, however, with Townsend's and Bailey's data, particularly in the case of argon, where the free path of electrons depends greatly on velocity.

scholarly journals The absorption coefficient for slow electrons in mercury vapour

1929 ◽  
Vol 125 (796) ◽  
pp. 134-142 ◽  
Keyword(s):  
Absorption Coefficient ◽  
Path Length ◽  
Mean Free Path ◽  
Mercury Vapour ◽  
Cross Sectional ◽  
Original Apparatus ◽  
Maximum Angle ◽  
The Mean ◽  
Slow Electrons ◽  
Good Agreement

The effective cross-sectional area of an atom is defined in this paper as that area within which a passing electron is deflected so that it can no longer go through a system of slits defining a beam of electrons. The sum of all these areas in a cubic centimetre of the gas defines the absorption coefficient, the reciprocal of which is the mean free path. The absorption coefficient is a function of the atom studied and the velocity of the electron. It way also depend on the geometry of the apparatus which defines the maximum angle of deflection. From the agreement of the results obtained by several observers with different limiting angles, the variation of the observed absorption coefficient with size of the limiting angle appears to be small. The absorption coefficient is compound from the equation I = I 0 e -α xp , where I is the electron current at the end of the path, I 0 the current at the beginning of the path, x the path length, p the pressure of the gas α the absorption coefficient. Apparatus .—For the measurement of the absorption coefficient a modification of Ramsauer's original apparatus was used. The same modification was previously used for the measurement of the absorption coefficient in other gases giving results in good agreement with those by Ramsauer's more complicated apparatus.

Nuclear Absorption of Low-Energy Pions

1971 ◽  
Vol 49 (9) ◽  
pp. 1211-1214 ◽  
Author(s):  
Douglas S. Beder
Keyword(s):  
Numerical Calculation ◽  
Nuclear Matter ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Absorption Rate ◽  
Mean Free Path ◽  
Low Energy ◽  
Absorption Cross ◽  
Nuclear Absorption ◽  
The Mean

We derive an expression for the mean free path of low energy π's traversing nuclear matter, assuming that absorption is dominantly on nucleon pairs. Relating the absorption cross section to the data for the inverse reaction NN → NNπ makes this susceptible to numerical calculation. We also discuss how properly to account for nucleon Fermi motion in calculating the absorption rate.

scholarly journals The absorption coefficient for slow electrons in the vapours of mercury, cadmium and zinc

1925 ◽  
Vol 109 (750) ◽  
pp. 397-405 ◽  
Keyword(s):  
Absorption Coefficient ◽  
Electric Fields ◽  
Single Molecule ◽  
Unit Volume ◽  
Effective Area ◽  
Classical Dynamics ◽  
The Common ◽  
The Mean ◽  
Slow Electrons ◽  
Unit Pressure

According to the classical dynamics, the molecules in the path of a beam of electrons will, by virtue of their electric fields, deflect the electrons constituting the beam. This deflection, while not perceptible for the electrons which pass at large distances from the molecule, may cause those which approach more closely to disappear from the beam. The effective area, within which an electron will be deflected from the beam, can be calculated from the equation I = I 0 e -α xp , where I 0 is the number of electrons initially present in the beam, I the number remaining at the end of the path x , p the pressure of the gas, and α the absorption coefficient or the effective stopping area of all the molecules in a unit volume of gas at unit pressure. The mean effective area of a single molecule is obtained by dividing a by 3·56 × 10 16 , when the units chosen are millimetres of Hg and centimetres. Using this equation, Lenard and others have determined the absorption coefficients for most of the common gases.

Sign in / Sign up

Export Citation Format

Share Document