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Author Topic: Do electrons capture nucleons?  (Read 4107 times)

Online jeffreyH

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Do electrons capture nucleons?
« on: 06/09/2014 16:37:51 »
When considering that an electron can be captured by a nucleus can we say that the force applied on the proton by an electron can be viewed as the electron also 'capturing' the proton?


 

Offline JP

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Re: Do electrons capture nucleons?
« Reply #1 on: 06/09/2014 19:33:19 »
I suppose you could view it that way, but it's not usually used in practice.  The nucleus is so much more massive than the electron that it is pretty much just sitting there while the electron gets pulled in. 

It's a bit like how we generally assume the earth is orbiting the sun, although in reality, you could say the sun is orbiting the earth (or more correctly, that both are in orbit about a common center of mass).  But in practice, we can almost always neglect the sun's motion in response to the earth since it's just so much more massive.
 

Offline PmbPhy

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Re: Do electrons capture nucleons?
« Reply #2 on: 06/09/2014 19:39:27 »
When considering that an electron can be captured by a nucleus can we say that the force applied on the proton by an electron can be viewed as the electron also 'capturing' the proton?
I think that on this one we can say its pure semantics. Does a truck hit a flea or does a flea hit a truck kind of thing.
 

Online jeffreyH

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Re: Do electrons capture nucleons?
« Reply #3 on: 06/09/2014 21:01:44 »
I know that the effect could be considered insignificant. The equal and opposite charges have always puzzled me since the masses differ so much.
 

Offline alancalverd

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Re: Do electrons capture nucleons?
« Reply #4 on: 06/09/2014 21:09:56 »
Why so? You can add the same (or equal and opposite) charges to a football and a pea, and a neutron has pretty much the same mass as a proton but no charge at all.
 

Online jeffreyH

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Re: Do electrons capture nucleons?
« Reply #5 on: 06/09/2014 22:30:56 »
Why so? You can add the same (or equal and opposite) charges to a football and a pea, and a neutron has pretty much the same mass as a proton but no charge at all.

Yes but the charge does not originate in a football or a pea. It originates in a particle.
 

Offline UltimateTheory

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Re: Do electrons capture nucleons?
« Reply #6 on: 06/09/2014 22:33:48 »
When considering that an electron can be captured by a nucleus can we say that the force applied on the proton by an electron can be viewed as the electron also 'capturing' the proton?

Do you realize that free proton has 1836.15 times more mass than electron.. ?
(free proton doesn't capture electron normally)

Your question is like whether "Earth is capturing meteor" or "meteor is capturing Earth"...

The first nucleus capable to capture electron is Be-7 via reaction:
Beryllium-7 + e- -> Lithium-7 + Ve + 0.861893 MeV
So mass ratio between electron and that nucleus is even higher. 12786.7 times more mass than electron.
« Last Edit: 06/09/2014 22:36:22 by UltimateTheory »
 

Offline allan marsh

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Re: Do electrons capture nucleons?
« Reply #7 on: 06/09/2014 22:45:31 »
Sounds as if hydrogen is a figment of imagination?
 

Offline alancalverd

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Re: Do electrons capture nucleons?
« Reply #8 on: 07/09/2014 18:32:09 »


Yes but the charge does not originate in a football or a pea. It originates in a particle.

If you separate a football and a pea, previously in contact, you will probably find equal and opposite charges on them. 
 

Online jeffreyH

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Re: Do electrons capture nucleons?
« Reply #9 on: 07/09/2014 20:55:31 »


Yes but the charge does not originate in a football or a pea. It originates in a particle.

If you separate a football and a pea, previously in contact, you will probably find equal and opposite charges on them.

That may be so but then we are considering macroscopic objects and not even solid objects, simply objects in contact with no inter-molecular bonds. This says nothing about short range microscopic effects where the charge originates.
 

Online evan_au

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Re: Do electrons capture nucleons?
« Reply #10 on: 08/09/2014 12:26:11 »
Quote
The equal and opposite charges have always puzzled me

The equal (but opposite) charge on proton & electron has puzzled many theoretical physicists.

It has been experimentally confirmed that the elementary charge is equal in magnitude, to within a very small fraction.
However, there is apparently nothing the the Standard Model that requires them to be equal in magnitude (but our universe would be very different if they were different!).

This hints at a deeper symmetry, below the current Standard Model of subatomic particles.
 

Online jeffreyH

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Re: Do electrons capture nucleons?
« Reply #11 on: 09/09/2014 00:05:26 »
Quote
The equal and opposite charges have always puzzled me

The equal (but opposite) charge on proton & electron has puzzled many theoretical physicists.

It has been experimentally confirmed that the elementary charge is equal in magnitude, to within a very small fraction.
However, there is apparently nothing the the Standard Model that requires them to be equal in magnitude (but our universe would be very different if they were different!).

This hints at a deeper symmetry, below the current Standard Model of subatomic particles.

I seem to be typing Klingon as no one else got the point. I can't remember the exact details now but the energy of the electron was originally a problem and its rotation would either have had to be at or exceed light speed. I beleive this was resolved by spin 1/2. There always has to be a balance in a system and if the balance is not equal mass it has to be of some other property.
 

Offline alancalverd

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Re: Do electrons capture nucleons?
« Reply #12 on: 09/09/2014 07:39:34 »
That's the problem of using a classical model to describe an atom. It just ain't so, and we invent quantum mechanics to describe and predict (but not explain) what actually happens.

Anyway the answer to the original question is "yes, sort of". If you fire a proton beam into a material, the protons interact with the electrons in the target and slow down. But neutron-electron interaction is much weaker and it is the proton density of the target that determines its absorption, which is why we use water or polyethylene as a neutron shield.
 

Online jeffreyH

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Re: Do electrons capture nucleons?
« Reply #13 on: 09/09/2014 17:28:28 »
I have been looking around for information on photon/neutron interactions but all the sites I found dealt with radiation and not with direct interaction between the two particles. I would expect this to be a weak interaction too but I don't know without any data.
 

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Re: Do electrons capture nucleons?
« Reply #13 on: 09/09/2014 17:28:28 »

 

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