Positronium Decay: Energy of Photon?

  • Context: Graduate 
  • Thread starter Thread starter integrale2
  • Start date Start date
  • Tags Tags
    Decay
Click For Summary

Discussion Overview

The discussion revolves around the decay of positronium, specifically focusing on the energy of the photons produced during this decay process. Participants explore the implications of binding energy and rest mass in the context of photon energy calculations.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about the energy of photons resulting from the decay of positronium at rest, suggesting that the energy of each photon might equal the rest mass energy of the electron due to the small binding energy of positronium.
  • Another participant provides a translation and emphasizes the importance of the binding energy in determining photon energy, questioning how it should be factored into calculations.
  • A participant corrects the phrasing regarding the motion of the electron and positron, reinforcing the concept of them orbiting around their center of mass.
  • One participant reiterates the idea that the energy of a photon is equivalent to the rest mass of the electron, while also considering the binding energy as a negative value, suggesting that this would result in a slightly lower photon energy.
  • A later reply confirms the previous participant's assertion regarding the binding energy's effect on photon energy.

Areas of Agreement / Disagreement

There is some agreement on the relationship between photon energy and the rest mass of the electron, particularly regarding the impact of binding energy. However, the discussion includes varying interpretations of how binding energy should be accounted for, indicating that multiple views remain on this topic.

Contextual Notes

Participants express uncertainty about the exact calculations involved, particularly in relation to the binding energy and its negative contribution to photon energy. The discussion does not resolve these uncertainties.

Who May Find This Useful

This discussion may be of interest to those studying particle physics, quantum mechanics, or anyone looking to understand the nuances of positronium decay and photon energy calculations.

integrale2
Messages
3
Reaction score
0
Hi, i would like about the decay of positronium (a electron and a positron going around the center of mass) in 2 photons: if i suppose the positronium decays at the rest, what is the energy of photons?
I think that the energy of a photon is the same of mass of rest of electron, because the binding energy of positronium is very small with respect to mass of electron at the rest.
If i would like to not neglect the binding energy of positronium, what is the nergy of photon?
Thanks
 
Physics news on Phys.org
translation:

Hi, i would like [to know?] about the decay of positronium (a[n] electron and a positron [orbiting their] center of mass) in[to] 2 photons: if i suppose the positronium decays [while] at ... rest, what is the energy of [the resulting] photons?
I think that the energy of [each resulting] photon is the same [as the rest] mass ... of [the] electron, because the binding energy of positronium is very small with respect to [the rest] mass of [the] electron...
If i would like to [take into consideration] the binding energy of positronium, what is the energy of [each] photon?
Thanks
http://en.wikipedia.org/wiki/Positronium
Annihilation can proceed via a number of channels each producing one or more gamma rays. The gamma rays are produced with a total energy of 1022 keV (since each of the annihilating particles have mass of 511 keV/c²), the most probable annihilation channels produce two or three photons, depending on the relative spin configuration of the electron and positron. A single photon decay is only possible if another body (e.g. an electron) is in the vicinity of the annihilating positronium to which some of the energy from the annihilation event may be transferred. Up to five annihilation gamma rays have been observed in laboratory experiments[5], confirming the predictions of quantum electrodynamics to very high order.
 
Last edited:
Hi, thanks for the translation, but I think it is a mistake to eliminate around: "an electron and a positron [orbiting] AROUND their center of mass...
In "http://www.wordreference.com/definition/orbit", i find this example: "The moon orbits AROUND the Earth"...
and what do you think from a physical point of view about:
"If i would like to take into consideration the binding energy of positronium, what is the energy of each photon?"
 
Last edited by a moderator:
integrale2 said:
I think that the energy of a photon is the same of mass of rest of electron, because the binding energy of positronium is very small with respect to mass of electron at the rest.
If i would like to not neglect the binding energy of positronium, what is the nergy of photon?
Thanks

Before decay, the energy is

[m c2 for electron] + [m c2 for positron] + [binding energy]

Afterwards, we have

2 x [energy of one photon]

Since you know all quantities in the equation except the photon energy, it can be solved. If you're still stuck, post again.
 
Hi, I am in complete agreement upon which you wrote, I still have a little doubt, that is the core of my dilemma: the binding energy of course must be considered negative and then the energy of a photon is slightly lower the rest mass of electronics. E 'right?
 
Yes, that's right.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
5K
  • · Replies 32 ·
2
Replies
32
Views
5K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 3 ·
Replies
3
Views
4K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 15 ·
Replies
15
Views
7K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 15 ·
Replies
15
Views
4K
  • · Replies 4 ·
Replies
4
Views
5K