Resonance in electron impact on atoms

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Discussion Overview

The discussion revolves around the concept of resonance levels in the context of electron collisions with atoms, particularly focusing on how these resonance levels differ from other excited states. Participants explore the significance of resonance in electron-atom interactions and its implications for atomic excitation levels.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants inquire about the definition and significance of resonance levels when electrons collide with atoms, questioning how these levels differ from other excited states.
  • One participant suggests that resonance occurs when two frequencies match, leading to larger oscillation amplitudes, and seeks clarification on how this applies to excited atomic levels.
  • A participant provides an example using Xenon, detailing its ground and excited states, and proposes that levels with the same angular momentum value (J) might be considered resonance levels.
  • Another participant explains that for electron-atom collisions, energy versus cross-section plots can illustrate how the excitation cross-section changes with incident electron energy, noting that a peak in this plot represents a resonance peak.
  • It is mentioned that the excitation cross-section for certain states may reach a maximum at specific resonance levels, prompting further inquiry into the relationship between these states and resonance peaks.

Areas of Agreement / Disagreement

The discussion contains multiple competing views regarding the definition and implications of resonance levels, with no consensus reached on how these levels are specifically characterized or their significance in the context of atomic excitation.

Contextual Notes

Participants express uncertainty about the relationship between resonance levels and angular momentum values, as well as the specific characteristics of energy versus cross-section plots in this context.

Who May Find This Useful

This discussion may be of interest to those studying atomic physics, particularly in the areas of electron interactions, resonance phenomena, and atomic excitation processes.

vrinda mukund
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Can someone please explain the significance of resonance levels that forms when electron collides with atoms. How this resonance levels are different from other levels ?
 
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You should be able to answer that from the meaning of "resonance".
Have a go, and then we' all be able to help you better.
 
@Simon Bridge

Dear Sir,

When two frequencies match together so that the system oscillates at larger amplitudes, we say the system is in resonance. My doubt is how it is applicable to excited levels. Are they the levels with the same value for angular momentum J ? I that case, what makes it so special or different from other excited states.
To be more elaborate on my problem :

Ground state of Xenon is 5s2 5p6
First excited state for Xenon will be 5p6 6s1
If we write the term symbols the there will be five states :
1P1 3P0 3P1 and 3P2
Now, the states 1P1 and 3P1 are resonance levels.
So what i have guessed is levels with same value for J are said to be resonance levels . Is it really so ? How is it different from other levels 3P0 and 3P2
 
When two frequencies match together so that the system oscillates at larger amplitudes, we say the system is in resonance.
... close:
If you make a plot of the amplitude vs driving frequency for a driven oscilator, you get a characteristic peak near the natural frequency of the oscillator. That peak is called "a resonance".

My doubt is how it is applicable to excited levels.
... in the case of electrons being shot at some atoms, what is the graph that would be plotted? What shape would it have?
 
For electron-atom collisions, we can make energy Vs Cross section plots. We can plot how the cross section of a particular reaction, say excitation, changes with increasing energy of incident electron. The cross section will first increase with increase in energy and then will fall down.
 
Well done - between the "increase" and "fall down" there is a peak; that peak is called a "resonance peak".
We say that the particular process that the cross-section is for has a resonance at the energy level of the peak.
That is basically the entire significance of "resonance" in this context.
 
In that case, in the example of Xenon, which i explained before, is it like, the excitation cross section for excitation to the 5p5 6s1 levels will be maximum when electrons are excited to 1P1 and 3P1 states ?
 

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