Do just electrons emit photons?

[sophiecentaur]

questions about the categories of transitions

Personally, I always see categorising as seriously getting in the way of understanding. Your first category (electrons producing photons) is not a realistic one (for the reasons you have been given by me and others). The vibrational category is limited to isolated molecules (at least, the way you are thinking of it). Can you suggest a rotational transition that can exist at all in a solid?
This is your own personal sub-set of Physics and I suggest you read a (modern) textbook that deals with the solid state and that may give you a clue as to why your model doesn't explain enough of what we see around us.
You want to use your model to explain black body radiation. A monatomic gas at high temperature cannot produce a black body spectrum. The colours you would see if you took an envelope of Hydrogen gas and somehow put it in thermal equilibrium (i.e. heat it up) in a furnace at 1000°C. Would you expect it to be 'red hot'?
Yo get black body spectrum, you need a condensed arrangement of atoms so that transitions are 'available' amongst all the energy bands. This stuff is way beyond the elementary behaviour of idealised gaseous atoms and molecules.

 

[desta41]

To get black body spectrum, you need a condensed arrangement of atoms so that transitions are 'available' amongst all the energy bands. This stuff is way beyond the elementary behaviour of idealised gaseous atoms and molecules.

When it comes to all solids, I've seen things as a collective: condensed atoms and molecules (a lattice). For liquids and very dense gases: relatively condensed atoms and molecules (without a lattice). And dilute gases: isolated atoms and molecules.

Also, from what I've been studying as of late, the correct definition for vibration of condensed atoms and molecules, in a solid, would be 'vibrational modes' (involving phonons) vs. vibrational transitions (i.e. the category of) and that it's these vibrational modes that are responsible for blackbody radiation. Would this be a more accurate way of describing things (vs. the wording I'd been using prior to now)?

Another thing. I've seen a number of sources state that blackbody radiation also occurs from liquids and very dense gases, despite the fact that things aren't as condensed (as with solids). So, then, do liquids and very dense gases involve vibrational modes or just the categories of electronic, vibrational, and rotational? And if it's just the categories, then how could blackbody radiation be possible from liquids and very dense gases?

 

[sophiecentaur]

how could blackbody radiation be possible from liquids and very dense gases

Have you understood (i.e. could you reproduce the arguments) everything about the solid state/ I would recommend that you get totally sorted in that direction before you try to get to grips with the sort of statistics involved with liquids and gases under pressure. I suspect you may be just ticking things off a list, rather than learning stuff. Categorising things in this way doesn't get one far in the direction of 'understanding'. In the end it's the actual numbers involved that determine how things work.

 

[desta41]

Have you understood (i.e. could you reproduce the arguments) everything about the solid state/ I would recommend that you get totally sorted in that direction before you try to get to grips with the sort of statistics involved with liquids and gases under pressure. I suspect you may be just ticking things off a list, rather than learning stuff.

You know, I've seen users in various related forums ask questions that show much less study and thought put into their area of interest/concern and get treated with more respect than that which you've shown me. If you'd chosen to be more focused, in your posts, on helping me with straight-forward type answers vs. criticizing me at every turn and trying to size me up -- and making claims about me that are flat out wrong, this would have been a much more pleasant experience. But, instead, it's been a pretty demeaning one, at times, and especially in regard to my last post ('ticking things off a list, rather than leaning stuff' -- really?).

I lead an extremely busy life and am trying to take in as much knowledge as I can, in the little spare time I have, regarding certain areas of science in which I have a very deep interest. We all go about our learning differently due to lifestyle, time constraints, etc. As I said before, the approach you've taken with me is not appreciated and very non-constructive.

One important emergent, collective property that a solid has that are not found in isolated atoms and molecules is presence of phonons. This is a vibrational modes of a solid due to the gazillion atoms and molecules that make up the solid.

Moving on, it was ZapperZ, who in an earlier post discussed the matter of vibrational modes and phonons and absorbtion/emission. It was overlooked by me, at the time, due to a number of other issues I was involved with (both related and unrelated).

I've given a lot of time to the matter over the past day, researching, and have come to see that what ZapperZ was talking about answers a lot (helped put the pieces together much better). I feel as if I've been led into the right direction and have a better perspective on the matter.

So my last question in the last paragraph of my last post, which was a very good one, by the way, didn't warrant such a response (neither did). Simply not productive.

To ZapperZ (and equally to DrClaude): Those are the kinds of answers I appreciate. Straight forward and with a great attitude. Much appreciated!

 

[sophiecentaur]

As I said before, the approach you've taken with me is not appreciated and very non-constructive.

I must admit that I have been letting myself get too ratty with you. I apologise.
However, you say that you have little time to study this stuff and it is clear that you are trying to hurry too fast through the topic. (A lot of time"today" is hardly a big effort, is it?) it?)If you really don't have much time then I think you should accept that you will make slow progress. Nothing at all wrong with that. It's much more worth while to get a good grounding of basic stuff than to have a whistle stop tour through stuff that you are not in a position to grasp. You need to respect the subject more. It is not easy - why else do you think it took so long for many talented people to get the Science to where it is today? I am being very realistic here, you know.

 

[Andrew Mason]

If I take a bunch of protons and jiggle it up and down, I can generate light.

ANY accelerated charge will create EM radiation.

Zz.

Is a falling proton (under gravity) accelerating?

AM

 

[sophiecentaur]

Is a falling proton (under gravity) accelerating?

AM

Why not? The energy of the photon would be pretty low, of course and you would be hard put to actually detect it.

 

[rootone]

Is a falling proton (under gravity) accelerating?

AM

I think you probably meant 'photon' not 'proton'.
If that's the case then no, photons do not accelerate, they travel only at the speed of light.(They can gain energy by changing frequency though)
If you did mean protons, you are talking of hydrogen nucleii, they can be accelerated by gravity and also by electromagnetic fields.

 

[desta41]

A lot of time"today" is hardly a big effort, is it?) it?

You're killing me here :-/

Had just asked a question, that's all.

But, I can understand your viewpoint and what you're saying..

 

[sophiecentaur]

You're killing me here :-/

Had just asked a question, that's all.

But, I can understand your viewpoint and what you're saying..

But did you read the multitude of answers that told you the same thing? You just didn't seem to be taking it on board. QM is not just a five minute job. Go at it at a steady pace and you can be more certain of what you have learned. No short cuts, I'm afraid.
BTW, there is more to "Research" than finding some instant links on Google. Figuring out things on your own can be fun, you know.

 

[Andrew Mason]

I think you probably meant 'photon' not 'proton'.
If that's the case then no, photons do not accelerate, they travel only at the speed of light.(They can gain energy by changing frequency though)

No. I meant "proton".

If you did mean protons, you are talking of hydrogen nucleii, they can be accelerated by gravity and also by electromagnetic fields.

My question was in response to ZapperZ's post in which he stated ANY accelerating charge will create EM radiation. If falling protons are accelerating and if Einstein is correct that a falling proton is equivalent to a proton at rest in an inertial frame (which does not radiate) it seems that such an accelerating charge should not create EM radiation.

This seems to be one of the few areas in classical physics that is still somewhat controversial.

AM

 

[ZapperZ]

No. I meant "proton".

My question was in response to ZapperZ's post in which he stated ANY accelerating charge will create EM radiation. If falling protons are accelerating and if Einstein is correct that a falling proton is equivalent to a proton at rest in an inertial frame (which does not radiate) it seems that such an accelerating charge should not create EM radiation.

This seems to be one of the few areas in classical physics that is still somewhat controversial.

AM

I really didn't want to dive into that can of worms, simply because the OP has more basic, fundamental misunderstanding of simpler things (after all, I don't go after people every single time when they say that one can't get photoelectrons in a photoelectric effect with photons below the work function). There have been many papers addressing this very issue (is it still "controversial"?). The paper by Boulware is one I often read (D.G. Boulware, Annals of Physics, v.124, p.169 (1980)).

This should be in a separate thread if people still want to carry on with it.

Zz.

 

[desta41]

I really didn't want to dive into that can of worms, simply because the OP has more basic, fundamental misunderstanding of simpler things

I was referring to the whole, entire collective of an object (the system) and blackbody radiation (I made it very clear a number of posts back that I wasn't talking about an isolated molecule). Unfortunately, I've been misinterpreted throughout the latter half of this thread and portrayed as the one having a misunderstanding regarding that issue.

I know a solid object has an exponential amount of molecules and atoms all packed together (I suppose I'll be smacked down for saying that, as well, by a certain someone).

It's really a shame. I put in a lot of effort (in the little free time I have) when it comes to studying and get put through the ringer for asking a few questions. And then, when apologized to for the 'ratty' treatment, I get bizarrely criticized again in the next breath. And, a lot of this has been due to someone thinking I've been referring to an isolated molecule, all along, when I haven't.

 

[sophiecentaur]

put through the ringer for asking a few questions.

Not for asking questions but for ignoring the answers (not just mine but several others).
It is of no concern to me that you have very little study time but is does concern me that you would assume that it only requires a bit of time and effort to get to know this subject well. It does require a lot (and I mean a lot) of time (and a good programme of study) to get into this subject and there is no short cut. That is not a criticism, it's an observation which applies to everyone except the very occasional genius.

 

[PeterDonis]

desta41, the topic you are asking about is quite complex, but you seem to want to reduce it to a simple, small number of "ways a photon can be emitted". I don't think that's a fruitful strategy.

For example, the answer to the title question of this thread, as you ask it, is simple: "No." But the reason the answer is "no" is not that, oh, there isn't just one kind of thing that can emit photons (electrons), but three or four (electrons, molecular vibrations, rotations, ...). The reason the answer to your title question is "no" is that there are lots of different kinds of things that can emit photons, and it isn't useful to try to classify them into a small number of categories. If you want to understand this subject, you will need to spend enough time to learn about the complexities. As sophiecentaur says, there is no short cut.

 

[desta41]

ignoring the answers (not just mine but several others)

Acknowledging those answers that were, in fact, very helpful, and complementing the authors in the process, is hardly ignoring 'the answers'.

does concern me that you would assume that it only requires a bit of time

I never said that it requires a bit of time.

And, again, just to clarify, I wasn't speaking of an isolated molecule a while back. I was merely trying to understand the correct terminology to use when describing the whole system (without just saying 'whole system') that radiates blackbody radiation (which is a very good question, by the way).

If someone would like to answer that question properly, and simply, I believe I would be capable of understanding it. DrClaude gave a great answer, but it pertained to the isolated atoms and molecules. ZapperZ gave a great answer, but not sure if he meant the vibrational modes/phonons, only, as the cause to the blackbody radiation. From what I've been studying since, it looks like that may be only part of it (the vibrational modes). And, as for you, you've thought I've been referring to an isolated molecule all along when I haven't.

I am, in fact, talking about the entire system of an object and how to properly sum up what it is that's causing the radiation (lattice vibrations, an aggregate of the molecular vibrations, or a combination of both)? And to be honest, there just aren't sufficient answers on the Internet. So, I agree, a textbook would be of better help. When I have a good amount of time, I will be putting a lot more into this. But, in the meantime, it was just a question based on true, earnest study given the time and material at hand. That's all. A question.

I'm not asking for the world. I was just asking something pertaining to a particular area (and, yes, I realize the area as a whole will take a lot more time to understand). And I'm asking that you try to see that I was never talking about an isolated molecule.

 

[PeterDonis]

I was merely trying to understand the correct terminology to use when describing the whole system (without just saying 'whole system') that radiates blackbody radiation (which is a very good question, by the way).

The correct terminology to use, at the level of detail you're asking for in this thread, is that the whole system radiates blackbody radiation.

I am, in fact, talking about the entire system of an object and how to properly sum up what it is that's causing the radiation (lattice vibrations, an aggregate of the molecular vibrations, or a combination of both)?

A combination of both, plus a lot of other stuff, all of which can only be summed up in simple terms by saying "the whole system". Until you put in the time to study the subject in detail, that's really the best answer that you can get.

 

[desta41]

For example, the answer to the title question of this thread, as you ask it, is simple: "No." But the reason the answer is "no" is not that, oh, there isn't just one kind of thing that can emit photons (electrons), but three or four (electrons, molecular vibrations, rotations, ...).

I just saw your answer after typing my last post. Thank you. -- Both answers. I will go over what you just posted. Again, thank you.

 

[desta41]

A combination of both, plus a lot of other stuff, all of which can only be summed up in simple terms by saying "the whole system". Until you put in the time to study the subject in detail, that's really the best answer that you can get.

Thanks so much. I had a feeling it was more than just vibrational modes. And, as for the molecular vibrations, when I was speaking of those types of vibrations in the past, on this thread, I meant as an aggregate -- a whole. I never meant to give the impression that I was looking at it as an individual concept.

But I really appreciate your answer. And I am aware that I have a lot to study. Just hope to find the "right" books.

 

[blue_leaf77]

https://www.amazon.com/dp/0199573379/?tag=pfamazon01-20
You may want to look at chapter 8 and 10.

 

[desta41]

https://www.amazon.com/dp/0199573379/?tag=pfamazon01-20
You may want to look at chapter 8 and 10.

Thank you for suggesting that book and those specific chapters. And saw the write-up that says the book contains an up-to-date account of the optical physics of solid state materials. Very good..

 

[Alastair McD]

Hi desta41,

I am not surprised you are confused. Most of the answers you have got are misleading!

There are two types of radiation - continuum and line. Blackbody radiation is of the continuum type and the radiation produced by an electron changing state in a hydrogen atom is line radiation. Another type of continuum radaition is Bremsstralung (braking radiation). It is produced when an (high powered) electron hits an atom and is slowed as it approaches the positively charged nucleus. The loss of energy is converted into contnuum radiation. IMHO, blackbody radiation is produced by the vibrations in a solid causing the free electrons to bounce off the nucleii of the atoms, so producing continuum radiation in a similar fashion.

The classic line radiation is produced by the electron in an atom jumping from one quantum state to another, either as the result of absorbing the energy of a photon, or spontaneously and emitting a photon equal to its loss of energy. That is at a fairly high energies so only occurs as visible light.

Molecules can also absorb and emit photons, but only if their rotations and/or vibrations cause their overall electromagnetic field to be distorted. Note that from this POV the electron is a cloud, not a particle, surrounging the nucleus. The energy levels of vibrations is in the infra red (IR). A hydrogen molecule does not have a distoted emf i.e. it does not have a dipole and is not IR active. When it vibrates, i..e. strtches, the emf remains symetrical, similarly for oxygen and nitrogen molecules. But when carbon dioxide vibrates it does create distorted field. The oxygen bonds can waggle and they can stretch asymetrically, and so it acts as a greenhouse gas.

It is all a matter of quantum mechanics, but it is not simple.

HTH,

Cheers, Alastair.

 

[desta41]

Another type of continuum radaition is Bremsstralung (braking radiation). It is produced when an (high powered) electron hits an atom and is slowed as it approaches the positively charged nucleus.

I remember studying up on braking radiation. I appreciate your putting this into perspective for when it comes to continuum radiation.

Molecules can also absorb and emit photons, but only if their rotations and/or vibrations cause their overall electromagnetic field to be distorted. Note that from this POV the electron is a cloud, not a particle, surrounging the nucleus. The energy levels of vibrations is in the infra red (IR). A hydrogen molecule does not have a distoted emf i.e. it does not have a dipole and is not IR active. When it vibrates, i..e. strtches, the emf remains symetrical, similarly for oxygen and nitrogen molecules. But when carbon dioxide vibrates it does create distorted field. The oxygen bonds can waggle and they can stretch asymetrically, and so it acts as a greenhouse gas.

Very clearly stated, and makes sense. Thank you for taking the time.

 

[ZapperZ]

Wait till you visit a synchrotron light source or an FEL and see how such a facility generate light. You'll see why my claim of shaking charge up and down is relevant.

Zz.

 

[mfb]

Synchrotron radiation from accelerated protons is a significant issue in the LHC.

 

[desta41]

You'll see why my claim of shaking charge up and down is relevant

I absolutely hear you

 

[Ralph Dratman]

When atoms and molecules are clumped together into a solid, they form a conglomerate in which the characteristics of the solid are predominately due to the collective behavior of all these atoms and molecules. What that means is that the individual behavior of the atoms and molecules are often no longer apparent in the properties of the solids.

Is radio frequency emission from a wire antenna an example of the type of collective behavior you refer to? I ask because I have not been able to find a description of antenna behavior, whether transmitting or receiving, from a quantum viewpoint. Everything about antennas seems to be discussed from a purely classical EM perspective. I don't doubt that this is the right practical approach, but I would like to see some kind of quantum treatment, if only a simple-minded description of the process by which photons are emitted from the wire.

 

[ZapperZ]

Is radio frequency emission from a wire antenna an example of the type of collective behavior you refer to? I ask because I have not been able to find a description of antenna behavior, whether transmitting or receiving, from a quantum viewpoint. Everything about antennas seems to be discussed from a purely classical EM perspective. I don't doubt that this is the right practical approach, but I would like to see some kind of quantum treatment, if only a simple-minded description of the process by which photons are emitted from the wire.

No, it is not. An antenna is described in classical E&M and a boundary condition problem. However, it shares similarities with the jiggling charge that I mentioned.

Zz.

 

[PeterDonis]

I would like to see some kind of quantum treatment, if only a simple-minded description of the process by which photons are emitted from the wire.

You're assuming that the EM field in question can be usefully modeled as "photons emitted from the wire". As I understand it, the EM wave state that is emitted is very different from the kinds of EM states that the term "photon" can be usefully applied to. (For one thing, AFAIK the wave state is not an eigenstate of the photon number operator.)