Why are the peaks in the Franck-Hertz experiment broad?

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SUMMARY

The discussion focuses on the broadening of peaks observed in the Franck-Hertz experiment, specifically when using helium gas. It establishes that while energy levels are discrete, factors such as Doppler broadening from atomic motion and stochastic variations in electron collisions contribute to the observed peak broadening. The relationship between accelerating voltage and current is highlighted, indicating that the expected discrete energy levels are affected by these broadening mechanisms.

PREREQUISITES
  • Understanding of the Franck-Hertz experiment
  • Knowledge of atomic energy levels and their discreteness
  • Familiarity with Doppler broadening concepts
  • Basic principles of electron collisions in atomic physics
NEXT STEPS
  • Research the effects of Doppler broadening in spectroscopy
  • Study the statistical mechanics of electron-atom collisions
  • Explore the Franck-Hertz experiment with different gases
  • Learn about the implications of peak broadening on experimental data interpretation
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Physics students, experimental physicists, and researchers interested in atomic interactions and spectroscopy will benefit from this discussion.

tayles123
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As opposed to discrete values, given that the energy levels are discrete.

The gas in mind here is helium.

When studying the peaks a plot of accelerating voltage vs current that match up to the energy levels they should be discrete, right?
 
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Doppler broadening due to atomic motion will smear an otherwise sharp spectrum. Also I think some of the broadening may be due to the stochastic probability of an electron colliding with an atom. At each voltage, there is some variation in the number of collisions that occur, hence some noise in the data.
 

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