Is there plasma that doesn't radiate visible light? I think the

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Discussion Overview

The discussion centers around the characteristics of plasma, specifically whether plasma can exist without radiating visible light and the implications of having particles that are not atoms. Participants explore the nature of plasma, its composition, and the conditions under which it emits light, delving into theoretical and conceptual aspects.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants question whether plasma can exist without radiating visible light, particularly if it consists only of particles that are not atoms.
  • There is a suggestion that if plasma contains only uncharged particles, it may not emit light.
  • Others argue that charged particles in plasma can emit light through acceleration, regardless of atomic transitions.
  • Participants discuss examples of plasmas, including those with both nuclei and electrons, and those composed solely of ions.
  • Some express uncertainty about the definition of plasma, particularly regarding the requirement for overall electrical neutrality.
  • There are conflicting views on whether a plasma can consist solely of electrons or only of ions, with some participants providing definitions and examples to clarify their positions.
  • One participant mentions that high temperatures in plasma prevent electrons from being captured by atoms, suggesting that only positive ions could exist under certain conditions.
  • There is a discussion about the terminology used to describe ions and electrons in plasma, with some participants emphasizing the need for clarity to avoid confusion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether plasma can exist without radiating visible light or whether it can consist solely of electrons or ions. Multiple competing views are present regarding the definitions and characteristics of plasma.

Contextual Notes

Participants express uncertainty about the definitions of plasma and the conditions under which it can exist. There are unresolved questions about the implications of having only charged or uncharged particles in plasma.

Varon
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Is there plasma that doesn't radiate visible light? I think the electrons falling back to the nucleus radiate visible photons. But what if the plasma only has particles that are not atoms?
 
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Particles that are "not atoms"? Could you give us an example of what you have in mind?
 


rsr_life said:
Particles that are "not atoms"? Could you give us an example of what you have in mind?

I think he means that the particles in a plasma aren't bound into atoms, so do they radiate light. I believe they will emit various wavelengths of light due to accelerations of electrically charged particles. But I'm not sure.
 


Yes.. particles in plasma that aren't bound to atoms... what if they are not charged.. then they won't radiate? Or do all plasma contain charged particles?
 


Varon said:
Yes.. particles in plasma that aren't bound to atoms... what if they are not charged.. then they won't radiate? Or do all plasma contain charged particles?

You will not have a plasma on Earth that isn't made up of charged particles. The only place that could would be inside massive objects such as stars. And even then not really, as a free neutron has a half life of 15 minutes.
 


What are examples of plasmas that only contain electrons? Since there is no nucleus to make it fall to lower state, then no photons would be radiated, right? Then this plasma is totally invisible to visible spectrum?
 


Varon said:
What are examples of plasmas that only contain electrons? Since there is no nucleus to make it fall to lower state, then no photons would be radiated, right? Then this plasma is totally invisible to visible spectrum?

Er... an atomic transition is NOT the only way to create light. A charge particle being accelerated is another example. What do you think synchrotron light sources are? Or what about free electron lasers? You pass bunches of electrons through something that causes it to wiggle up and down, and viola! You get light!

Zz.
 


i see. what plasma sources have both nucleus and electrons in the plasma and what plasma sources have pure ions only? Any site with a list of them?
 


Varon said:
i see. what plasma sources have both nucleus and electrons in the plasma

Your fluorescent lamps.

and what plasma sources have pure ions only?

The ion beam at RHIC, ion beam milling equipment, etc.. etc.

Zz.
 
  • #10


ZapperZ said:
Your fluorescent lamps.



The ion beam at RHIC, ion beam milling equipment, etc.. etc.

Zz.

I thought that a plasma was defined as having net neutral charge.
 
  • #11


sophiecentaur said:
I thought that a plasma was defined as having net neutral charge.

I don't think that's a necessary criteria, is it?

If it is, then asking for "ion beam plasma" would be an oxymoron, which probably won't surprise me.

Zz.
 
  • #12


Varon said:
Is there plasma that doesn't radiate visible light? I think the electrons falling back to the nucleus radiate visible photons. But what if the plasma only has particles that are not atoms?

Does solar wind radiate visible light? How about a household air ionizer?

Respectfully,
Steve
 
  • #13


ZapperZ said:
I don't think that's a necessary criteria, is it?

If it is, then asking for "ion beam plasma" would be an oxymoron, which probably won't surprise me.

Zz.

I wouldn't normally just quote Wikkers but they, and a few other more raggedy sites, seem to reckon that a plasma is overall neutrally charged.

It wouldn't be the first oxymoron I'd come across!:smile:
 
  • #14


Wiki entry on Plasma stated:

"Definition of a plasma

Plasma is loosely described as an electrically neutral medium of positive and negative particles (i.e. the overall charge of a plasma is roughly zero)."

Is this true?

So overall charge is roughly zero for plasma composed of atoms? And for those composed only of ions.. it's negative charge? Is this correct? So how do each of them (neutral and charged) behave? What is the major (dramatic) difference between them aside from charge?
 
  • #15


How can you conclude that a plasma can consist of only Ions if you are quoting an article saying a plasma is neutral?
 
  • #16


Zapper mentions about ion plasma beam.. which I assumed is negative charged since it is composed of electrons
 
  • #17


You are assuming Zapper is correct?
 
  • #18


sophiecentaur said:
You are assuming Zapper is correct?

He is PF Mentor, How could he be wrong. If he is not sure, he would say not sure.
 
  • #19


Er... being a PF Mentor doesn't make it right all the time. In fact, I think sophiecentaur may have a more accurate definition of a "plasma" than what I had assumed.

Zz.
 
  • #20


Varon said:
Zapper mentions about ion plasma beam.. which I assumed is negative charged since it is composed of electrons

Er... "ion beam" is composed of ions, not electrons.

You asked for a "plasma" consisting only of ions, and I gave you an ion beam. This may or may not be a valid example of a "plasma". That's why if a plasma is a net neutral gas, I said that asking for an "ion plasma" is an oxymoron.

Zz.
 
  • #21


ZapperZ said:
Er... "ion beam" is composed of ions, not electrons.

You asked for a "plasma" consisting only of ions, and I gave you an ion beam. This may or may not be a valid example of a "plasma". That's why if a plasma is a net neutral gas, I said that asking for an "ion plasma" is an oxymoron.

Zz.

Oh. I thought an electron is an ion. Anyway, wiki says:

"An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative".

Can plasma can be composed of positive or negative ions?
 
  • #22


Varon said:
Oh. I thought an electron is an ion. Anyway, wiki says:

"An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative".

Can plasma can be composed of positive or negative ions?

Here's my look on it.

Generally speaking, an Ion is an atom, or at least a nucleus of an atom. A single electron isn't generally considered an Ion since it is a fundamental particle, while Ions in plasmas can be anything from 1 proton to heavy nuclei consisting of tens - hundreds of nucleons. This gives rise to calling electrons in plasma by their actual name and calling the nuclei by the term Ions, since calling them anything else doesn't really make sense to me. Also, calling an electron an Ion would probably add confusion when talking about plasmas since they are negatively charged while the protons and nuclei are positive. Probably just another way to help differentiate the two charges in plasmas.
 
  • #23


Has anyone mentioned that only positive ions could exist in a plasma because the temperature will mean that passing electrons cannot get captured by an atom. Their energy will be too high.
 
  • #24


sophiecentaur said:
Has anyone mentioned that only positive ions could exist in a plasma because the temperature will mean that passing electrons cannot get captured by an atom. Their energy will be too high.

If not, then you just did!
 
  • #25


In my earlier message. I asked if plasma can contain ions only (at that time I thought ions are electrons) so I didn't get the answer I seek. So let me ask again, can plasma be composed of electrons only? What if you get a group of electrons and heat them... won't they be plasma?
 
  • #26


Varon said:
In my earlier message. I asked if plasma can contain ions only (at that time I thought ions are electrons) so I didn't get the answer I seek. So let me ask again, can plasma be composed of electrons only? What if you get a group of electrons and heat them... won't they be plasma?

Offhand I would call that plasma, but I am unsure about the scientific/technical world.
 
  • #27


Honestly, does it really matter what its CALLED? Is that all you were wanting to know or did you have something else to go along with that?
 
  • #28


Did you not read the definition of a plasma? If you did then did you not get the bit about electrical neutrality? If a plasma is neutral then don't you need both positive and negative charges in there?
How did you intend to get the electrons to all stay together without some positive ions around to stop them drifting off?
 
  • #29


Drakkith said:
Honestly, does it really matter what its CALLED?

Perhaps not but if we aren't all talking with the same terms then any conversation is a bit limited.
Certainly there is a huge difference between a neutral mixture and a large group of particles all with the same charge.
 
  • #30


sophiecentaur said:
Did you not read the definition of a plasma? If you did then did you not get the bit about electrical neutrality? If a plasma is neutral then don't you need both positive and negative charges in there?
How did you intend to get the electrons to all stay together without some positive ions around to stop them drifting off?

Ok. I just heard some theorize that dark matter is composed of plasma and wondering what kind of unconvensional particles it may contain that don't react electromagnetically... or too subtle to be detected... they reported about magnetic field that exist right in the middle of nowhere in deep outer space... and wondered if they came from the dark matter plasma..
 

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