Physics Lab Equipment

LEAI-35 Apparatus of Ramsauer-Townsen Effect

LEAI-35 Apparatus of Ramsauer-Townsen Effect

Note: liquid Nitrogen not provided


  • Easy to use with compact structure

  • Ample experimental examples

  • Stable performance


In 1912, German physicist C. Ramsauer discovered the collision cross section of an electron with gas atoms is related to the speed of the electron. When the electron energy is relatively high, the scattering section of an Argon atom increases with a decrease in electron energy. But when the electron energy is less than a dozen eV, the scattering section decreases rapidly with a decrease in electron energy. In 1922, British physicist J. Townsend found a similar phenomenon. In classical theory, scattering section is independent of the speed of an electron, while Ramsauer and Townsend's experimental results indicate an opposite theory, which can only be explained by quantum mechanics.  


This Ramsauer-Townsen effect experimental apparatus can measure IS-VA and IP-VA curves, and determine the relationship between scattering probability and electron speed. The instruction manual contains comprehensive materials including experimental configurations, principles and step-by-step instructions. Please click Experiment Theory and Contents to find more information about this apparatus.


Using this apparatus, the following experiments can be completed:


1. Understand the collision rule of electrons with atoms and learn how to measure atomic scattering cross section.

2. Measure scattering probability versus speed of low-energy electrons collided with gas atoms.

3. Calculate the effective elastic scattering cross section of gas atoms.

4. Determine the electron energy of the minimum scattering probability or scattering cross section.

5. Verify the Ramsauer-Townsend effect, and explain it with the theory of quantum mechanics.



Voltage supplies

filament voltage0 ~ 5 V adjustable
accelerating voltage0 ~ 15 V adjustable
compensating voltage

0 ~ 5 V adjustable

Micro current meters

transmissive current3 scales: 2 μA, 20 μA, 200 μA, 3-1/2 digits
scattering current4 scales: 20 μA, 200 μA, 2 mA, 20 mA, 3-1/2 digits
Electron collision tubeXe gas
AC oscilloscope observationeffective value of acceleration voltage: 0 V-10 V adjustable

Parts List

Power supply1
Measurement unit1
Electron collision tube2
Base and stand1
Vacuum flask1
Instructional manual1

       Apparatus of Ramsauer-Townsen Effect.jpg

Schematic diagram of AC measurement

(Click figure to enlarge)

       Apparatus of Ramsauer-Townsen Effect.png

Schematic diagram of DC measurement

(Click figure to enlarge)

     Apparatus of Ramsauer-Townsen Effect.png

Relationship between electron scattering probability and square root of acceleration voltage

(Click figure to enlarge)

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