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Questions tagged [positronium]

Positronium (Ps) is an unstable exotic atom bound state consisting of an electron and its anti-particle, a positron. The orbit and energy levels of the two constituent leptons are analogous to, but significantly different than those of the hydrogen atom. May also use for similar systems such as muonium.

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Positronium radius more than expected

I am trying to derive the basic properties of positronium. Usually it is stated that we can just set reduced mass of hydrogen atom as $\dfrac{1}{2}m_e$ and obtain: \begin{equation} r_n=\dfrac{8\pi\...
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A question of spin in Electron Positron Anahilation

I have read the other questions dealing with the spin of the electron and positron, but have a slightly different question. Does the amount of energy produced in a E-/E+ collision depend on the spin ...
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Scalar positronium decay Feynman diagram

Charged scalar particles appear in some Beyond the Standard Model theories and are regularly searched for at high energy colliders. For positronium there is a simple Feynman diagram as shown below ...
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Question on positronium lifetime

From Wikipedia I could get that lifetime of orthopositronium (spin of electron and positron point in same direction) is $t=\frac{9h}{4m_ec^2\alpha^6(\pi^2-9)}$ And parapositronium $t=\frac{h}{\pi m_ec^...
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Darwin term in positronium

Darwin term in Hydrogen atom has the form (in natural units) $$ V_{Darwin}=\frac{\alpha}{8m^2} 4\pi \delta(\vec{r}) $$ My question is this: is the $m$ in the denominator electron mass, or the reduced ...
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Electron positron annihilation to more the 3 photons

I understood why a single photon can't be released from the annihilation of an electron and positron and that the common cases are 2 and 3 photons. I have two thing's I'm unsure of: why is the ...
Tomer Gigi's user avatar
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What kind of matter is positronium?

What kind of matter is positronium? Normal matter, antimatter, exotic matter or something else? We know: Matter is made up of electrons, protons and neutrons. Antimatter is made up of positrons, ...
Rajeev Ranjan Sharma's user avatar
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How did Ernest Sternglass’ phenomenologically incorrect model of the neutral pion predict its mass and lifetime so accurately?

In 1961, Ernest Sternglass published a paper where, using what seems to be to be a combination of relativistic kinematics and Bohr’s old quantisation procedure, he looked at the energy levels of a set ...
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Why do the electron and positron creation operators anti-commute?

I am learning QFT and is baffled by a minor problem. The electron and the positron should be distinguishable, as they have different charges. So why do their creation operators anti-commute? They ...
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Can we fully ionize an atom by annhilating its electrons with a positron beam?

I am unable to digest research papers on this topic so I am asking here. Can an atom be fully ionized by a positron beam through positron-electron annhilation? What are the limitations of this process ...
Akif Ismail's user avatar
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How to treat semi-relativistic bound states?

I’m interested in semi-relativistic bound state, positronium, bottomonium, charmonium, etc. One way to treat such bound states in relativistic QFT is Bethe-Salpeter equation: $$(\Box+m^2)(\Box +m^2) \...
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Why is the speed of light in vacuum frequency-independent?

I recently came across this paper: Mainland & Mulligan, Foundations of Physics 50(5), 457–480, "Polarization of Vacuum Fluctuations: Source of the Vacuum Permittivity and Speed of Light" ...
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Energy raise in positronium due to temporary annihilation

In Griffith book on elementary particles, page-162, it is written: In positronium, the positron and electron can annihilate temporarily giving rise to a virtual photon only when it is in a triplet ...
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On the size of positronium

How can we simply apply the bohr model on a positronium as the positronium doesn't even have a nucleus or nucleus-like entity like in a hydrogen like atom. Moreover this implies that the first ...
Schwarz Kugelblitz's user avatar
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How would a cloud of ortho-positronium atoms behave near a magnetic dipole?

The force on a macroscopic magnetic dipole with dipole moment $\mathbf{m}$ in an inhomogeneous magnetic field $\mathbf{B}(\mathbf{r})$ is given by $$\mathbf{F} =\nabla (\mathbf{m} \cdot \mathbf{B}(\...
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What is the atomic number of a positronium?

Since a positronium has no proton, I would suggest $Z = 0$ but I'm not sure if you can see the electron as the center of mass and therefore $Z = 1$.
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Would cooling matter and antimatter to as close to Absolute Zero as possible allow them to coexist?

I was reading about Bose-Einstein condensates and how they affect matter and energy, and I wondered if "draining" that amount of energy from an atom of hydrogen and positronium would potentially allow ...
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Time and frequency extremes

I wonder if there exists a table of which physical events have the shortest time scale (like matter/antimatter annihilation) and which have the longest (like proton decay). The same question applies ...
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Photon emission between an electron and positron

If I placed and electron and a positron at a certain distance apart in a vaccumm, they would attract each other and annihilate producing 2 or more gamma rays. But, what I would like to know is, does ...
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Bohr's model and positronium

I was trying to get an order of magnitude estimate for the radii and energies of positronium using the Bohr's model. I did find a few places where they have used the reduced mass to replace the ...
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What is $r$ in angular momentum quantization rule?

We know $$mvr= nh/2π $$ What is $r$ here if I consider positronium system. I suppose it should be the radius of the orbit in which both are moving. But when I take the above equation and electrostatic ...
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Size of positronium

Positronium consists of an electron and a positron. By what factor is a positronium atom bigger than a hydrogen atom? The solution has been explained to me. The characteristic length when solving for ...
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Positronium energy level in QED

I'd like to know if it is possible to compute positronium mass and lifetime from a QED approach. I'm searching for some literature on how to treat resonances in QED (or general QFT) ; most of the ...
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Single Photon emission from positronium in strong magnetic fields; how is momentum conserved?

I recently came across a paper (which I will not describe in detail, however, the authors examine the probability of positronium producing a single photon, while under the influence of a strong ...
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Stability of the hydrogen atom and positronium

I am trying to get a better understanding of why positronium decays while a hydrigen atom is stable. In the case of positronium, I can write an elementary process were the leptons annihilate into two ...
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Why positronium can annihilate in vacuum?

I thought that the annihilation process of positronium cannot take place without a third-party particle. This can be directly derived from energy & momentum conservation: energy conservation: $$h\...
Janek_Kozicki's user avatar
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How is the centre of mass of a Positronium associated with that of an electron and positron?

How is the centre of mass of a Positronium likely associated with that of an electron and positron?
monisha_4's user avatar
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Why does positronium decay into 2 photons more often than into 3 photons?

I cannot find the answer to the above question. I know that para-positronium is created with a probability of $25\%$ and decays into 2 photons, while ortho-positronium is created with a probability ...
Johanna Anna's user avatar
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materials that repel positrons?

In this article is discussed at some length positron formation in metallic surfaces. Positrons have work functions that describe how much energy they have to receive in order to be extracted from the ...
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Does positronium have a stable crystalline phase?

I wonder if there is a way to stabilize and store positronium in a way that the mass of storage device is negligible to the antimatter fuel It is known that excited Ps atoms with high n (rydberg or ...
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positronium BEC stability

After reading this article regarding Positronium BEC formation (for lasing purposes), there is a mention in there regarding Ps "up" atoms not annihilating with "down" atoms, the article is pretty ...
lurscher's user avatar
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