Units of Electron Volts (AMeV)

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Discussion Overview

The discussion revolves around the meaning and usage of the unit AMeV in the context of space weather and nuclear physics. Participants explore its implications for energy measurements related to atomic nuclei and the potential confusion surrounding its notation.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant suggests that A in AMeV may refer to atomic mass, relating to the energies of ions rather than single electrons.
  • Another participant asserts that A represents the mass number of a nucleus, providing an example with Carbon nuclei to illustrate the concept.
  • Some participants question whether the unit should relate to the atomic (proton) number instead of the mass number, noting that neutrons are not accelerated by voltage.
  • A participant proposes that AMeV units provide energy-per-nucleon, which is significant for nuclear reactions, comparing energies of different nuclei.
  • There is mention of confusion in the literature regarding the notation of AMeV, with some participants noting the absence of space between A and MeV.
  • One participant expresses uncertainty about available literature that clarifies the usage of AMeV.
  • A later reply questions whether the unit might be better expressed as MeV/A.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of A in AMeV, with no consensus reached on its definitive meaning or the appropriate notation. The discussion remains unresolved regarding the clarity and standardization of the unit.

Contextual Notes

Participants highlight potential confusion stemming from notation practices in physics literature, including the use of spaces and italics, which may affect understanding of the unit.

GreenLRan
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Hi,
I have been viewing some publications related to space weather and have noticed that in many graphs and in the articles, the units AMeV appear very often. I am wondering what the A is for?

My best guess is that means atomic, ie relating energies of ions rather than single electrons. Does anyone know for certain. If so, can you provide proof or documentation?

Thank you!
 
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A is the mass number of a nucleus. So if a Carbon nuclei has 1 A MeV, it has a total energy of 12 MeV since A=12 for Carbon.
 
That's weird. If an eV is the energy of a single electronic charge which has been accelerated across 1V PD then it will be the same for all singly charged objects. If the atom is multiply ionised then the energy would be higher, natch, but would it not relate to the Atomic (Proton) Number, rather than the Mass Number? (The Neutrons are not accelerated by the V, after all)
All this is only applicable under pretty extreme generating conditions, I guess.
 
hi Norman,
is there any book explain it. because i notice in particle physics journal many author ref it as AMev or AMeV, without a space between A/A and MeV. I also just curious about this unit confusion..
thanks
 
sophiecentaur said:
That's weird. If an eV is the energy of a single electronic charge which has been accelerated across 1V PD then it will be the same for all singly charged objects. If the atom is multiply ionised then the energy would be higher, natch, but would it not relate to the Atomic (Proton) Number, rather than the Mass Number? (The Neutrons are not accelerated by the V, after all)
All this is only applicable under pretty extreme generating conditions, I guess.

I think the rational for AMeV units is that it gives the energy-per-nucleon, an important quantity to know for nuclear reactions. For example a 12 MeV C-12 nucleus is comparable to a 56 MeV Fe-56 nucleus. Different total energies, but each has the same 1 AMeV.
 
Rajini said:
hi Norman,
is there any book explain it. because i notice in particle physics journal many author ref it as AMev or AMeV, without a space between A/A and MeV. I also just curious about this unit confusion..
thanks

I don't know of any books off hand that cover the subject (there might be some older nuclear physics books that I am not familiar with that look at it). Much of your confusion is simply sloppy notation which is very common the physics literature and which I am often guilty of. Typically there is no space between the A and MeV. And whether A is italicized or not is likely due to whether the author is using italic letters to denote variables or not.
 
So does that mean that this unit have been better expressed as MeV/A ?
 

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