Reaction Q value and threshold energy

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Discussion Overview

The discussion revolves around the calculation of the energy of a reaction's ejectile, particularly focusing on the role of the reaction Q value and threshold energy in scenarios where the Q value is negative. Participants explore how these concepts interact in the context of conservation of energy and momentum.

Discussion Character

  • Technical explanation, Debate/contested

Main Points Raised

  • One participant questions whether the threshold energy must be considered when calculating the energy of the ejectile if the Q value is negative.
  • Another participant asserts that the energy of incoming particles must be sufficient to meet the threshold, indicating that threshold energy is relevant in calculations.
  • A different participant suggests that if the incoming particle's energy exceeds the threshold, the focus should shift to the energy of the particle rather than the threshold energy, while acknowledging the negative Q value's relevance.
  • Another reply reiterates that both the energy of the particle and the threshold energy are relevant, linking the negative Q value closely to the threshold energy.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of threshold energy versus the energy of the incoming particle in calculations, indicating that the discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants do not clarify the specific conditions under which the threshold energy and Q value interact, leaving some assumptions and dependencies on definitions unaddressed.

oksuz_
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In order to calculate the energy of a reaction's ejectile, we make use of the concepts of the conservation of energy and momentum along with the reaction Q energy. However, if there is a threshold energy with above zero, meaning Q value is negative, do we have to consider the threshold energy as we calculate the energy of the ejectile?

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The energy of the incoming particles has to be high enough to meet this threshold, and the threshold energy enters the calculations.
 
If the incoming particle's energy is higher than the threshold energy, then we should consider the energy of the particle, not the threshold energy, should not we? And also Q-value enters the calculations, but it is, in this circumstances, negative. Am I right?
 
oksuz_ said:
then we should consider the energy of the particle, not the threshold energy, should not we?
Both are relevant.
oksuz_ said:
And also Q-value enters the calculations, but it is, in this circumstances, negative.
That is very closely linked to the threshold energy.
 

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