Can a positron shield an antiproton so that it can catalyse fusion?

[Wo Wala Moiz]

TL;DR Summary

Decreasing the annihilation cross-section of antiproton using the shielding effect of a positron to catalyse fusion

An antiproton cannot be used to practically catalyse fusion because the annihilation cross-section between it and a reactant nuclei is greater than the fusion cross-section between the reactant nuclei [1]. Can a positron bound to the antiproton reduce the annihilation cross-section adequately to facilitate fusion catalysis?

[1] https://inis.iaea.org/collection/NCLCollectionStore/_Public/27/007/27007232.pdf

 

[anuttarasammyak]

Muon catalyzing fusion has a history of investigation which could make positive nulcears to come closer. Is the idea which you suggest along to muon catalyzing fusion to any extent ?

 

[Wo Wala Moiz]

Muon catalyzing fusion has a history of investigation which could make positive nulcears to come closer. Is the idea which you suggest along to muon catalyzing fusion to any extent ?

Yes, but antiproton catalysed fusion has already been investigated, and because of annihilation probabilities, it cannot catalyse more than a single fusion event on average per antiproton.

Thus, my idea is to use a positron to shield the antiproton so the probability of the annihilation is decreased, while still increasing the chances of fusion at low temperatures.

 

[snorkack]

Consider the symmetry between matter and antimatter.
A positron should have exact same effect of shielding between proton and antiproton as electron does.

 

[Wo Wala Moiz]

Consider the symmetry between matter and antimatter.
A positron should have exact same effect of shielding between proton and antiproton as electron does.

Suppose we substitute the positron-antiproton system interacting with two naked reactant nuclei, with an antiproton simply introduced into a collection of hydrogen-2 molecules (twice the electrons, twice the shielding. Shouldn't effect the much heavier antiproton's effect too much...)

In my scenario, the two reactant nuclei would move into the first orbital of the antiproton with the position in an outer orbital. It is possible in this configuration for the annihilation to be less likely to occur because the positron's shielding will increase the distance between the nuclei and the antiproton.
In the second scenario, the two reactant nuclei would have a covalent configuration with the antiproton and two electrons in the middle. As a result, the antiproton will always be closer to both reactant nuclei than the reactant nuclei will be to each other.

 

[anuttarasammyak]

Thus, my idea is to use a positron to shield the antiproton so the probability of the annihilation is decreased, while still increasing the chances of fusion at low temperatures.

Thus made anti hydrogen atom is neutral so its effect is limited, I am afraid.

 

[Wo Wala Moiz]

If we have two hydrogen atoms, they will react to form a hydrogen molecule even at zero kelvin. They will also release a lot of heat. This is because, despite being neutral, they still have a dipole electric field. Monoatomic hydrogen is very unstable.

Thus made anti hydrogen atom is neutral so its effect is limited, I am afraid.

 

[snorkack]

If we have two hydrogen atoms, they will react to form a hydrogen molecule even at zero kelvin. They will also release a lot of heat. This is because, despite being neutral, they still have a dipole electric field. Monoatomic hydrogen is very unstable.

Monoatomic hydrogen is quite stable at low pressures.
The reason is that when you have two hydrogen atoms at zero kelvin, or 2,7 kelvin, they have great trouble reacting to form a hydrogen molecule. They need to release 4,52 eV energy, but they cannot because hydrogen molecule (with two electrons) is due to symmetry forbidden from emitting photons by vibration or rotation. Which is why there is far too many hydrogen atoms in the world, and not nearly enough hydrogen molecules, save in dense and dusty clouds.

 

[Wo Wala Moiz]

Monoatomic hydrogen is quite stable at low pressures.
The reason is that when you have two hydrogen atoms at zero kelvin, or 2,7 kelvin, they have great trouble reacting to form a hydrogen molecule. They need to release 4,52 eV energy, but they cannot because hydrogen molecule (with two electrons) is due to symmetry forbidden from emitting photons by vibration or rotation. Which is why there is far too many hydrogen atoms in the world, and not nearly enough hydrogen molecules, save in dense and dusty clouds.

There I go asserting stuff I guestimate is true. Thanks for the correction.

My point is that a technically neutral system can still participate vigorously in reactions.

 

[anuttarasammyak]

This is because, despite being neutral, they still have a dipole electric field.

Hydrogen atom has no dipole electric field which is not necessary for covalent bond to take place.

 

[Wo Wala Moiz]

Hydrogen atom has no dipole electric field which is not necessary for covalent bond to take place.

It absolutely does. The nuclei is positive. The electrons are negative.

Covalent bonds form because of the electric field of the atoms involved. What do you think holds the electrons in place?

The electrons move between the nuclei because of the attractive force, and the nuclei are held together by mutual attraction to the electrons.

 

[renormalize]

It absolutely does. The nuclei is positive. The electrons are negative.

That's simply wrong. The quantum ground-state (electron cloud) of an isolated hydrogen atom $H$ is spherically-symmetric and thus has no dipole moment. And even though the electron cloud of hydrogen molecules $H_2$ is not spherically-symmetric, they too have no dipole moment (https://cccbdb.nist.gov/diplistx.asp).

 

[Wo Wala Moiz]

That's simply wrong. The quantum ground-state (electron cloud) of an isolated hydrogen atom $H$ is spherically-symmetric and thus has no dipole moment. And even though the electron cloud of hydrogen molecules $H_2$ is not spherically-symmetric, they too have no dipole moment (https://cccbdb.nist.gov/diplistx.asp).

Then how are chemical bonds mediated?

I won't argue against scientific data. I would guess that the dipole is induced by interaction with other particles (an excited state).

 

[snorkack]

Then how are chemical bonds mediated?

I won't argue against scientific data. I would guess that the dipole is induced by interaction with other particles (an excited state).

The chemical bond between two hydrogens in a neutral molecule (two electrons) is stable and strong if formed. The problem is that if you start with two neutral hydrogen atoms (one electron each), there is no way to form the bond because there is nowhere to put the energy. Likewise, if you have a hydrogen molecule which is excited by vibration or rotation, it is strongly forbidden from emitting away its excitation energy because of the symmetry.
Forbidden excitations do have some small branches of decaying, but the most easier way to deexcite is by collision with some extra particle.

 

[Wo Wala Moiz]

The chemical bond between two hydrogens in a neutral molecule (two electrons) is stable and strong if formed. The problem is that if you start with two neutral hydrogen atoms (one electron each), there is no way to form the bond because there is nowhere to put the energy. Likewise, if you have a hydrogen molecule which is excited by vibration or rotation, it is strongly forbidden from emitting away its excitation energy because of the symmetry.
Forbidden excitations do have some small branches of decaying, but the most easier way to deexcite is by collision with some extra particle.

Can't the newly formed hydrogen molecule be deexcited by the emission of a photon?

 

[snorkack]

Can't the newly formed hydrogen molecule be deexcited by the emission of a photon?

That´s what is forbidden by lack of transition dipole moment.

 

[Wo Wala Moiz]

So in the absence of another particle absorbing the energy, two monatomic hydrogen particles will form a brief bond which will instantly decay?

 

[snorkack]

So in the absence of another particle absorbing the energy, two monatomic hydrogen particles will form a brief bond which will instantly decay?

Roughly, yes. They bounce off each other.

 

[Wo Wala Moiz]

Roughly, yes. They bounce off each other.

If we had a naked proton and monoatomic hydrogen particle, would they form a bond?

 

[snorkack]

If we had a naked proton and monoatomic hydrogen particle, would they form a bond?

I think they would.
Dihydrogen cation (one electron for the two protons) is the simplest two nucleus system. It has a binding energy of about 2,8 eV relative to lone proton and separate hydrogen atom. As for radiation, I think the asymmetry between proton and a hydrogen atom provides the transition dipole moment that a pair of identical neutral hydrogen atoms lack.

 

[Wo Wala Moiz]

I think they would.
Dihydrogen cation (one electron for the two protons) is the simplest two nucleus system. It has a binding energy of about 2,8 eV relative to lone proton and separate hydrogen atom. As for radiation, I think the asymmetry between proton and a hydrogen atom provides the transition dipole moment that a pair of identical neutral hydrogen atoms lack.

So would an antihydrogen atom be able to capture deuterons?

 

[mfb]

Not really "capture", but its antiproton can annihilate with the deuterium. It's easier without the positron around - it gives the electrostatic attraction a larger useful range.

 

[snorkack]

Not really "capture", but its antiproton can annihilate with the deuterium. It's easier without the positron around - it gives the electrostatic attraction a larger useful range.

Capture is what enables annihilation, unless the nuclei collide at low angular momentum.

So would an antihydrogen atom be able to capture deuterons?

Apply symmetry operation. It is symmetric to a hydrogen atom capturing an antideuteron.
Consider what happens if a hydrogen atom meets a negative particle!
When a hydrogen atom meets a second electron, it gets bound with a binding energy of about 0,75 eV. Both electrons will be equal.
But when a hydrogen atom meets a muon, the muon because of its mass can approach closer to the nucleus than an electron can. As the muon approaches the nucleus, the electron gets unbound and expelled.
I therefore conclude that just like a muon, an antiproton or an antideuteron would expel the electron from a hydrogen atom.

 

[Wo Wala Moiz]

Not really "capture", but its antiproton can annihilate with the deuterium. It's easier without the positron around - it gives the electrostatic attraction a larger useful range.

The point is for the antiproton to be used to be used in fusion catalysis. Annihilation is undesirable.

 

[mfb]

Well, but annihilation is the process that happens.

The positron is irrelevant for the nuclear processes.

 

[snorkack]

Well, but annihilation is the process that happens.

The positron is irrelevant for the nuclear processes.

On the final approach, that is. Due to symmetry, you can follow the same reasoning with electron.
When a muon, or antiproton, or any other negative particle (there are lots - tauon, pion, kaon, D and B mesons, Σ, Ξ and Ω hyperons, some anti-Λ) approaches the nucleus at a larger distance, the nucleus of a neutral atom is mainly shielded by the electron, so the attraction to negative particle is far weaker than that of lone nucleus would be. But not none. Atom is polarizable by the external field, and the nucleus is not fully shielded. So as the massive negative particle approaches the nucleus, the electron being much less massive is repelled and displaced from the nucleus.

If you want to hamper an antiproton from annihilating with the proton, you better shield the proton with a massive negative particle. More massive than the antiproton. Such as a tauon, or something beautiful (but check that your beautiful meson or hyperon does not itself react with the proton).

 

[Wo Wala Moiz]

Capture is what enables annihilation, unless the nuclei collide at low angular momentum.

Apply symmetry operation. It is symmetric to a hydrogen atom capturing an antideuteron.
Consider what happens if a hydrogen atom meets a negative particle!
When a hydrogen atom meets a second electron, it gets bound with a binding energy of about 0,75 eV. Both electrons will be equal.
But when a hydrogen atom meets a muon, the muon because of its mass can approach closer to the nucleus than an electron can. As the muon approaches the nucleus, the electron gets unbound and expelled.
I therefore conclude that just like a muon, an antiproton or an antideuteron would expel the electron from a hydrogen atom.

Can I get a citation for this?

 

[Wo Wala Moiz]

Well, but annihilation is the process that happens.

The positron is irrelevant for the nuclear processes.

The positron is meant to reduce the probability of annihilation. With the antiproton being so massive, it may still bring the two reactant nuclei closer than even a muon.

 

[snorkack]

Can I get a citation for this?

https://link.springer.com/chapter/10.1007/978-1-4613-3042-4_10

It was a lot of hard work to grant your request. Just because a fact is memorable and backed by respectable reasoning and references where encountered does NOT mean that it is easy to generate a useful search string from the fact.

That´s why the site policy against questions based on "heard it somewhere" is problematic.

 

[Wo Wala Moiz]

https://link.springer.com/chapter/10.1007/978-1-4613-3042-4_10

It was a lot of hard work to grant your request. Just because a fact is memorable and backed by respectable reasoning and references where encountered does NOT mean that it is easy to generate a useful search string from the fact.

That´s why the site policy against questions based on "heard it somewhere" is problematic.

I wish I could add more than a like for your efforts. Maybe this will suffice?



Also, are you aware of Sci-Hub?