Does an electron have a makeup

[ryn17]

While this question might seem ignorant to some I have not yet come across any literature that addresses and solves it.
The question is, has anyone cracked open an electron to see what it is made of ? I ask because if it is more than one particle; couldn't it's internal reactions serve to cause a wobbling in a double slit experiment making it appear to have wave like properties.While the electron is propelled in a straight line it would almost certainly wobble before it hit the receiver even in a "vacuum".
also I have yet to find a double slit experiment which it has been made apparent that it was done in a vacuum.If anyone can post a link that would be great

 

[dextercioby]

The question is, has anyone cracked open an electron to see what it is made of ?

I will answer to the only question reasonable,which doesn't include speculations.
No.My guess is,they never will.In the Standard Model of Particles and Interactions,the electron is a fundamental particle,just like the others.Among the massive particles (let's exclude neutrino(s),it's still fuzzy),it has the smallest mass,therefore,roughly speaking,it has no other massive particles to decay into.Therefore it is a stable particle,just like the photon and all other fundamental particles.
So far,no experiment has indicated an internal structure for the electron.

Daniel.

 

[Schneibster]

While this question might seem ignorant to some I have not yet come across any literature that addresses and solves it.
The question is, has anyone cracked open an electron to see what it is made of ?

As far as anyone knows, and according to the theory called QED, no, and they never will. An electron is a very simple beast; it doesn't have many characteristics. It's so simple that you can't tell one from another, literally. It's single reason for existence appears to be that it is the lightest particle that can carry an electric charge.

I ask because if it is more than one particle; couldn't it's internal reactions serve to cause a wobbling in a double slit experiment making it appear to have wave like properties.While the electron is propelled in a straight line it would almost certainly wobble before it hit the receiver even in a "vacuum".
also I have yet to find a double slit experiment which it has been made known that it was done in a vacuum.
any info will be greatly appreciated

No one has ever seen anything remotely like this, and if it was there they couldn't have missed it.

I don't know if the dual slit experiment has been explicitly done with electrons, but you see diffraction and interference of them every time you turn on your computer monitor. We know all about it, and them. We have to, or the monitor doesn't work and you aren't reading this, and I'm not writing it.

 

[jtbell]

I don't know if the dual slit experiment has been explicitly done with electrons [...]

A Google search for "double slit experiment with electrons" produces this as one of the first hits:

http://physicsweb.org/articles/world/15/9/1

 

[chrismuktar]

This is an easy question to answer.

The electron has no internal structure because it has an infinite lifetime. By this I mean it does not decay to any lower order components. We can show this is true because we know what all the other reactions of the electron should be and they fit together like a puzzle, if there were another decay mode, it wouldn't fit.

The electron is a 'lepton', meaning that it is considered to be a point particle with zero volume. This idea is strongly support by experiment. Be aware not to confuse wavefunction (probability) with the 'size'.
Chris.

 

[reilly]

Protons and neutrons do have structure. There is no sign that they "wobble". If electrons wobbled, then electron accelerators would not work, nor, for that matter, would proton accelerators.

Also, I'm not sure that wobbling electrons would work in an electron microscope.
Regards,
Reilly Atkinson

 

[marlon]

While this question might seem ignorant to some I have not yet come across any literature that addresses and solves it.
The question is, has anyone cracked open an electron to see what it is made of ? I ask because if it is more than one particle; couldn't it's internal reactions serve to cause a wobbling in a double slit experiment making it appear to have wave like properties.While the electron is propelled in a straight line it would almost certainly wobble before it hit the receiver even in a "vacuum".
also I have yet to find a double slit experiment which it has been made apparent that it was done in a vacuum.If anyone can post a link that would be great

The Standard Model is the best theory that we have up till now when it comes to describing the properties of elementary particles (of which the electron is one); The electron does not have an internal structure for several reasons in this model. No experimental verification, no other elementary particles to decay into, no decay is possible because that would mess up the conservation laws that govern the weak interaction (eg : beta-decay) which are correctly bescribed by this modell. Also, no theory proves this possibility, in stead it is ruled out by the theory used to construct the standard model (eg field theories and group theory to govern the symmetries)...


regards
marlon

 

[reilly]

Yes indeed, electrons have been cracked open. To wit, consider the electron-positron beam collision experiments.
Regards,
Reilly Atkinson

 

[juvenal]

This is an easy question to answer.

The electron has no internal structure because it has an infinite lifetime. By this I mean it does not decay to any lower order components. We can show this is true because we know what all the other reactions of the electron should be and they fit together like a puzzle, if there were another decay mode, it wouldn't fit.

In the Standard Model, the proton doesn't decay either and has an infinite lifetime. Yet it has an internal structure.

 

[Entropy]

In the Standard Model, the proton doesn't decay either and has an infinite lifetime. Yet it has an internal structure.

Well, some think the proton may have an extremely long half-life, but I can't comment on the validity of that theory seeing how I don't know much about it.

As for an electron substructure. Closest thing you could say by today's knowledge would be strings.

I personally think we will discover an electron substructure in the future, but that's based on how I feel. But in the current model the electron doesn't need a substructure.

 

[sifeddin]

This is an easy question to answer.

... The electron is a 'lepton', meaning that it is considered to be a point particle with zero volume. This idea is strongly support by experiment. Be aware not to confuse wavefunction (probability) with the 'size'.
Chris.

An easy question to answer: I dought! However, I subscribe to your transaction.
Yet could you just give a link, or any documented reference to what you said and why the electron "should" be a "point" particle; because I only got this as "talkings"
BTW if you know the origin of the word "lepton" give me a hint. Any one but "dextercioby" is welcome to answer.

 

[lfanck]

The electron must have a substructure.

But in the current model the electron doesn't need a substructure.

To do not need a substructure dose not mean there is no substructure. If there is no substructure in electron, it is hard to explain how can an electron absorb a photon.

 

[ZapperZ]

To do not need a substructure dose not mean there is no substructure. If there is no substructure in electron, it is hard to explain how can an electron absorb a photon.

But an electron does NOT absorb a photon! You're confusing an atom absorbing a photon via an electronic transition versus an electron sitting around and absorbing a photon. The latter doesn't occur.

Darn it. We need to have an FAQ on this one.

Zz.

 

[marlon]

To do not need a substructure dose not mean there is no substructure. If there is no substructure in electron, it is hard to explain how can an electron absorb a photon.

This is a common misconception. An electron does NOT absorb a photon.
Photons can be absorbed by :

1) atoms : The energylevels of an electron in an atom are NOT the same as the energylevels of a single electron.

2) bulk materials like crystals, etc : the absorption occurs thanks to interaction with the phonons but NOT single atoms. The vibrational modes of the lattice vibrations absorb photons. So, this process is NOT the same as the one described in 1)

marlon

 

[Physics Monkey]

marlon and Zz,

Sorry guys, but what are you talking about? An electron can absorb a photon, it's the basic QED vertex. A simple physical example is Compton scattering.

 

[marlon]

The point is that a photon cannot be absorbed by a free electron. It can be scattered by a bunch of free electrons though. In the case of Compton scattering you do not get an absorption of photon by a free electron, so i don't get why you give this example.

marlon

edit : we have had this discussion here

 

[CarlB]

The standard model says that the electron has no substructure, this is true, but this hardly proves that the electron has no substructure.

There are a lot of complaints about the standard model, a primary one of them is that it has too many free parameters. In looking for a deeper theory, we must look around for any coincidences that appear among the parameters of the standard model.

For some examples of the coincidences, see:
http://arxiv.org/abs/hep-ph/0605074
http://arxiv.org/abs/hep-ph/0506094
http://arxiv.org/abs/hep-ph/0505220

Carl

 

[Physics Monkey]

marlon,

It is true that a real electron cannot emit or absorb a real photon without something else happening. However, the requirement that the electron be on shell is not at all essential, so electrons can absorb photons. Don't let the names fool you, the difference between real (on shell) electrons and virtual electrons is somewhat arbitrary and definitely subtle. I brought up Compton scattering because QED describes it in terms of electrons emitting and absorbing photons. The two leading order diagrams each involve an electron emitting one photon and absorbing one photon. In particular, the outgoing photon is not the same as the ingoing photon, but you can never tell because photons are identical.

I think I understand the point you and Zz were trying to make, and I agree that it is an often missed distinction. However, saying that electrons don't absorb photons is like telling the whole high energy physics community that their working language is nonsense.

 

[marlon]

marlon,

It is true that a real electron cannot emit or absorb a real photon without something else happening.

That is indeed the point.

However, the requirement that the electron be on shell is not at all essential, so electrons can absorb photons.

I don't follow. How about the conservation laws being violated (lepton number, J-momentum ?)

Don't let the names fool you, the difference between real (on shell) electrons and virtual electrons is somewhat arbitrary and definitely subtle.

I don't agree that the difference between real <---> virtual is arbitrary. I mean the definition based upon the fact that real particles are on mass shell is very straightforward. "The more" a particle is off mass shell, "the more" it is virtual. That is how i look at it and how i have always learned it.

I brought up Compton scattering because QED describes it in terms of electrons emitting and absorbing photons.

Correct but the electrons involved are not single free particles. That's why i had difficulties with your giving this example within the context of my first post.

However, saying that electrons don't absorb photons is like telling the whole high energy physics community that their working language is nonsense.

Well, to be honest when one speaks about "an electron", one refers to "one free electron". I know this can be debated but the general impression will be exactly this one. That is also why we get many such "electrons absorb photons"-misconceptions in this forum.

regards
marlon

 

[samalkhaiat]

But an electron does NOT absorb a photon!

Freeelectron does not absorb or emit photon. This is because of the law of conservation of energy and momentum (not the lepton number as suggested by somebody ).

You're confusing an atom absorbing a photon via an electronic transition

So what is it in the atom,other than electrons, that absorbs and emits photons?

Regards

sam

 

[Dense]

So what is it in the atom,other than electrons, that absorbs and emits photons?

Isn't it the transition of an electron from one energy level to another, which is what absorbs/emits a photon?

In other words, it's not the electron itself that absorbs the photon, but rather the system of its bond to the nucleus via coulomb forces.

And is there really such a thing as a "free" electron? Is a question about what a free electron can do just speculation?

 

[masudr]

This demonstrates how the sum of the parts are not equivalent to the whole.

 

[samalkhaiat]

Isn't it the transition of an electron from one energy level to another, which is what absorbs/emits a photon?

In other words, it's not the electron itself that absorbs the photon, but rather the system of its bond to the nucleus via coulomb forces.

The correct statement is:
The electron does absorb photon in the presence of the Coulomb field of the nucleus;
1) It is the electron's (not the coulomb field's) energy that is increased after the absorption.
2) It is the electron ( not the coulomb field) that interacts with photon.

And is there really such a thing as a "free" electron?

Yes, beta-particles.

regards

sam

 

[ZapperZ]

I think I understand the point you and Zz were trying to make, and I agree that it is an often missed distinction. However, saying that electrons don't absorb photons is like telling the whole high energy physics community that their working language is nonsense.

I currently am doing a "beam loading" experiment where a bunch of electrons in an RF photoinjector "sucks in" energy from that RF. Does this mean these electrons have absorbed these photons? Nope!

You need to keep in mind that when someone makes this kind of a statement, they mean a real photon being absorbed, because they are confusing an atomic transition to mean an electron absorbing that photon. I will put to you that in the majority (if not 100%) of the case, this is what is being confused. We're not talking about QED here, thank you, because chances are, people who make that kind of a statement are not even aware of such virtual interactions.

I think this is another example where things have been taken way out of context.

Zz.

 

[ZapperZ]

Isn't it the transition of an electron from one energy level to another, which is what absorbs/emits a photon?

In other words, it's not the electron itself that absorbs the photon, but rather the system of its bond to the nucleus via coulomb forces.

Correct. It is the WHOLE atom that gains in energy. The consequence of which is that one or more electrons make an electronic transition that obeys the dipole selection rule.

And is there really such a thing as a "free" electron? Is a question about what a free electron can do just speculation?

Particle accelerators, and to some extent, ordinary metals.

Zz.

 

[reilly]

If indeed electrons do not absorb photons, then I'm in big trouble. My doctoral dissertation involved QED -- computations of radiative corrections to various electron scattering experiments -- and I do talk about absorbtion and emission of photons not only by electrons, but by protons and neutrons as well. Not only that, but the entire literature of QFT is full of "emissions' and "absorbtions", often represented by Feynman diagrams. I agree with Physics MonkeyThe ideas of emission and absorbtion arise from canonical quantization in Fock Space, the usual creation and destruction operators in a 3-point interaction typically take a general form

B*(p+k) A(k) B(p)

where B* is a creation operator and B a destruction operator for a charged particle, and A is a destruction operator for a neutral boson -- photon, scalar meson, vector boson. From the origins of the subject,a standard way of describing such an interaction term is : a charged particle absorbs a photon and ups its momentum -- or absorbtion of a photon with momentum k, ...

The ideas of emission and absorbtion-- cf Einstein as well as Bohr, not to
mention Planck -- are best thought of as metaphors, rather than get tangled up with virtual and real and -- and that's how they are generally presented in most of QFT, and usefully so. (And, there are times when such metaphorical interpretations are not the best way to go.) And, as is so often the case, history gives a strong case for the standard interpretation of creation/destruction operators , not excluding Yukawa's ideas of particle exchange -- emit and absorb --
as a physical basis for a nuclear force.

Do we really need to rewrite most of the many, many QED texts?
Do I need to rewrite my thesis, and remove all those pesky "absorbtions"?

Regards,
Reilly

PS The anomalous magnetic moment of the electron gives proof of an electromagnetic structure for the electron.

 

[Physics Monkey]

marlon,

Conservation laws are not violated when an electron emits a photon. The QED vertex has built into it the various conservation laws. What is true is that the mass shell condition and the conservation laws cannot simultaneously be satisfied. In quantum field theory, it is the mass shell condition that goes out the window while the conservation laws remain firmly in place.

As for the difference between real and virtual, I agree that isn't totally arbitrary. It is, however, somewhat arbitrary. I don't have time to get into it right now, but even so called real particles cannot have definite energy otherwise they would live forever. Thus nothing is truly on the mass shell; the mass shell condition mimics what would be true in a classical world, but we don't live in such a world.

Regarding Compton scattering, I'm not sure what you mean when say the electron isn't free. Both the photon and the electron propagate freely until they interact at which point the electron absorbs the photon. That is the interpretation that the lowest order Feynman diagrams suggest. Of course, this is not to say that the electron is really doing that in the classical sense, this is just a convenient way to talk about a process with a certain amplitude.

Finally, my point is that people don't mean neccessarily mean a real electron when they say electron. Maybe condensed matter people always mean that (although I know that's not even true), but it is common in high energy physics to speak of electrons absorbing photons. For example, in Feynman's book QED, one of the basic actions of the universe is an electron emitting a photon.

 

[Physics Monkey]

I currently am doing a "beam loading" experiment where a bunch of electrons in an RF photoinjector "sucks in" energy from that RF. Does this mean these electrons have absorbed these photons? Nope!

You need to keep in mind that when someone makes this kind of a statement, they mean a real photon being absorbed, because they are confusing an atomic transition to mean an electron absorbing that photon. I will put to you that in the majority (if not 100%) of the case, this is what is being confused. We're not talking about QED here, thank you, because chances are, people who make that kind of a statement are not even aware of such virtual interactions.

I think this is another example where things have been taken way out of context.

Zz.

ZapperZ,

The only thing electrons do in QED is emit and absorb photons. Ok, they move around too I agree that there is a common misconception here, but one shouldn't compound that misconception by saying something which is untrue. Electrons do emit and absorb photons. Furthermore, when someone asks about photons, they are asking about QED whether they know it or not. If the person asking the question doesn't understand this, then the person answering the question should try to help them understand it. The point here is that while clearing up a misconception is wonderful, contradicting the most precise theory of electrons and photons available isn't.

 

[ZapperZ]

ZapperZ,

The only thing electrons do in QED is emit and absorb photons. Ok, they move around too I agree that there is a common misconception here, but one shouldn't compound that misconception by saying something which is untrue. Electrons do emit and absorb photons. Furthermore, when someone asks about photons, they are asking about QED whether they know it or not. If the person asking the question doesn't understand this, then the person answering the question should try to help them understand it. The point here is that while clearing up a misconception is wonderful, contradicting the most precise theory of electrons and photons available isn't.

I disagree. Because if you say that an electron can absorb photon and then just walk away, you are giving only half of the picture also within QED, and this is also a misconception.

We had another thread about someone asking if the HUP implies a violation of the conservation of energy. This is precisely the situation where a particle emit a virtual particle where during this period of time, there's "more" energy than there was before. So if you were to say "yes, an electron can emit a photon" and not qualify that at all with the rest of the story, you have just broken the conservation laws and imply that there is validity in claiming that this energy non-conservation is "real".

As with the issue of "relativistic mass", I'd rather err on the conservative side with regards to the context being asked. I will bet you that the person who made such a statement has no clue what QED is.

Zz.

 

[marlon]

the mass shell condition mimics what would be true in a classical world, but we don't live in such a world.

So what you are saying is this : being off mass shell is not equivalent to virtuality. A virtual particle is off mass shell but an off mass shell particle is not always virtual. Correct ? If so, can you give me an example of the latter case ?

Regarding Compton scattering, I'm not sure what you mean when say the electron isn't free.

What i meant to say was that the interaction does not involve a photon and ONE electron. The electrons are conduction band electrons. This is a many particles situation.

Finally, my point is that people don't mean neccessarily mean a real electron when they say electron. Maybe condensed matter people always mean that (although I know that's not even true), but it is common in high energy physics to speak of electrons absorbing photons. For example, in Feynman's book QED, one of the basic actions of the universe is an electron emitting a photon.

Again, i understand your point but i object to the "lingo". One cannot just speak about an electron emitting a photon because most people (that sure as hell do not know about QED) will think of this situation as one electron emitting a photon while NOTHING ELSE is happening. This is not true.


regards
marlon

 

[reilly]

With all due respect. What's the problem? (Physics Monkey is hitting the ball out of the park on this one.)

It's all about a metaphor. This metaphor is designed to help make sense out of the abstract operator calculus associated with Fock Space; and the related matrix mechanics approach to the harmonic oscillator by means of step operators-- and, how to make sense of how these two subjects can be combined to be field theory, and QED, and... In fact, Dirac devotes a section in his Quantum Mechanics to, of all things, "Emission and absorption of bosons" (Sec. 61 in my copy)

Further, once a sacred text of QED, Dirac's Sec. 64 is entitled, Emission, absorption, and scattering of radiation. His classic discussion of QED is chock full of "absorptions" and "emissions." (He may well have originated this terminology, to soften the abstractness of something like a(k)|k1,k2,...>

So, what is Dirac missing?

Metaphors are a form of figurative language, not meant to be precise, but designed rather to help folks build an inutitive understanding of something. To me, Feynman diagrams are of the same ilk. It's been common practice for 70+ years to talk about emission and absoption of bosons -- and by people who quite understand the ideas of virtual states , one form of which is a so-called virtual particle. But, the good thing about figurative language is that it allows virtual to be real and real to be virtual. The profession assumes any reader of such information has enough common sense to understand the figurative nature of the discussion.
Anyone ready to sleep on Zee's mattress?
Anyone ready to rewrite Dirac?

Reguards,
Reilly

 

[ZapperZ]

With all due respect. What's the problem? (Physics Monkey is hitting the ball out of the park on this one.)

It's all about a metaphor. This metaphor is designed to help make sense out of the abstract operator calculus associated with Fock Space; and the related matrix mechanics approach to the harmonic oscillator by means of step operators-- and, how to make sense of how these two subjects can be combined to be field theory, and QED, and... In fact, Dirac devotes a section in his Quantum Mechanics to, of all things, "Emission and absorption of bosons" (Sec. 61 in my copy)

But if I can show an electron emitting and absorbing a virtual phonon, does that mean I can simply put on blinders and start telling people that yes, an electron can not only emit and absorb photons without qualifications, but it can also emit and absorb phonons, spinons, magnons, bipolarons, etc... etc?

It is as silly for me to use QFT and then somehow justify that it is OK to start saying that an electron can emit and absorb all of these zoo of bosons. Where do you stop?

And BTW, I resent the fact that you seem to imply that I am ignorant of QFT/QED treatment on this. This isn't about knowing the material. It is about what is the appropriate response when someone who has no clue of QFT and QED says that "an electron can absorb a photon" due to the misrepresentation of the atomic absorption phenomenon!

Zz.

 

[Pickels]

To be honest, I thought that electrons themselves absorbed without the help of the atomic complex. This tread kinda clears up why free moving electrons arent always emitting photons to me.

 

[nrqed]

But if I can show an electron emitting and absorbing a virtual phonon,...
.

I am not specifically adressing ZapperZ in teh following and I am not trying to pour oil on fire, but here is an observation.
To be more specific, let's talk about real photons.

It seems to me legitimate to say that electrons do emit photons (wouldn't everybody agree that this is a fair description of what happens during bremsstrahlung?)
And if so, why couldn't electrons also absorb photons if they can emit ones?

I am not saying that I necessarily have the correct interpretation, I am honestly curious about whether any of these two statements could be refuted.

Regards

 

[ZapperZ]

I am not specifically adressing ZapperZ in teh following and I am not trying to pour oil on fire, but here is an observation.
To be more specific, let's talk about real photons.

It seems to me legitimate to say that electrons do emit photons (wouldn't everybody agree that this is a fair description of what happens during bremsstrahlung?)
And if so, why couldn't electrons also absorb photons if they can emit ones?

I am not saying that I necessarily have the correct interpretation, I am honestly curious about whether any of these two statements could be refuted.

Regards

When an electron is in a field, be it in electric or magnetic field, it can easily interact with those fields and emits photons without the need to violate any of the conservation laws. Again, I see this almost every week whenever we try to accelerate and decelerate bunches and bunches of "free" electrons in a particle accelerator.

The problem here is that when someone talks about an electron absorbing a photon, we are talking about something like the photoelectric effect where an object absorbs a photon, for real, or an atom absorbing a photon, causing an electronic transition. In each of these processes, for conservation laws to be preserved, a bunch of things are required. In a photoelectric effect, the lattice ions are required to provide the recoil momentum. In an atomic transition, it requires the electronic orbit to change by + or - 1 angular momentum dictated by the selection rule. In other words, something simply cannot just swallow a photon that easily.

Now this isn't the same as a scattering process where one can easily attribute and account for all the conservation laws simply by changing the energy of the scattered photon and electron, while preserving the angular momentum. This is what we do in accelerating structures to accelerate charge particles, even under conditions where the accelerating fields have wavelengths significantly larger than the particle's deBroglie wavelength.

Zz.