Note: liquid Nitrogen not provided
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.
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.
|filament voltage||0 ~ 5 V adjustable|
|accelerating voltage||0 ~ 15 V adjustable|
0 ~ 5 V adjustable
Micro current meters
|transmissive current||3 scales: 2 μA, 20 μA, 200 μA, 3-1/2 digits|
|scattering current||4 scales: 20 μA, 200 μA, 2 mA, 20 mA, 3-1/2 digits|
|Electron collision tube||Xe gas|
|AC oscilloscope observation||effective value of acceleration voltage: 0 V－10 V adjustable|
|Electron collision tube||2|
|Base and stand||1|
Schematic diagram of AC measurement
Schematic diagram of DC measurement
Relationship between electron scattering probability and square root of acceleration voltage