Elastic electron-atom collision effects in the Franck--Hertz experiment
In the Franck--Hertz experiment one observes the effect of inelastic collisions in which fixed quanta of energy are exchanged between electrons and atoms. It is shown here that one can also readily demonstrate with a Franck--Hertz apparatus energy-dependent features of the elastic collision cross section. For mercury vapor of sufficiently high pressure, elastic electron--atom collisions between the grid and the anode are able to energy analyze the electrons so that the characteristic peaks and troughs in the anode current are still observed without the traditional retarding field to separate off the lowest-energy electrons. This is because in mercury vapor the most energetic electrons have the longest mean free path, are more penetrating through the gas, and are the most likely electrons to reach the anode. The electron transport theory for this effect is developed and applied to a crude determination of the electron energy distribution. Not surprisingly, the electron energy distribution in this experiment consists of two electron groups separated in energy by 4--5 eV consistent with the known 6/sup 1/S-6/sup 3/P energy-level separation in mercury of 4.9 eV.
- Research Organization:
- Research School of Physical Sciences, Australian National University, Canberra, 2600, Australia
- OSTI ID:
- 5469859
- Journal Information:
- Am. J. Phys.; (United States), Vol. 51:12
- Country of Publication:
- United States
- Language:
- English
Similar Records
Electron spectroscopy using a Franck--Hertz tube
Electron impact excitation and uv emission in the Franck--Hertz experiment
Related Subjects
ELECTRON-ATOM COLLISIONS
ELASTIC SCATTERING
MERCURY
CROSS SECTIONS
ELECTRODES
ENERGY DEPENDENCE
ENERGY SPECTRA
LOW PRESSURE
MEAN FREE PATH
VAPOR PRESSURE
ATOM COLLISIONS
COLLISIONS
ELECTRON COLLISIONS
ELEMENTS
METALS
PHYSICAL PROPERTIES
SCATTERING
SPECTRA
THERMODYNAMIC PROPERTIES
640304* - Atomic
Molecular & Chemical Physics- Collision Phenomena