Can a plasma give off black body emission?

In summary, there is a debate whether the light emission from a single bubble sonoluminescence (SBSL) is truly black body or if it only appears to be so due to certain conditions. Some argue that the emission mechanism is bremsstrahlung with slight black body emission nature due to a range of kinetic energies within the plasma, while others believe it to be truly black body radiation. Further research is needed to fully understand the nature of SBSL light emission.
  • #1
rwooduk
762
59
This may seem like a strange question, I'm trying to differentiate between the spectra from a plasma and the spectra from a black body, is there a difference?

I'm thinking the spectrum from a plasma would be that of bremstrahhlung as it is ions flying everywhere, so it would not be possible for it to have the spectrum of a black body.

but wouldn't a plasma that was enclosed in an area be a black body?

if someone could help me differentiate it would be really appreciated,

thanks in advance

edit in particular this statement:

This emission mechanism turns out to be same as the black body radiation with finite absorption, which confirms that the principal mechanism of SBSL is bremsstrahlung with slight black body emission nature.

which makes very little sense to me, how can something be bremsstrahlung AND black body?
 
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  • #2
Plasmas are often very good approximations to black bodies (see stars like the sun as example).

If you integrate over the bremsstrahlung spectrum with the kinetic energy distributions, you might get something close to a thermal spectrum (not sure).
 
  • #3
mfb said:
Plasmas are often very good approximations to black bodies (see stars like the sun as example).

If you integrate over the bremsstrahlung spectrum with the kinetic energy distributions, you might get something close to a thermal spectrum (not sure).

Many thanks for that, yes stars did come to mind! Will look further into the integration you suggested thanks!

also it occurs to me that a plasma will be a VOLUME emitter, where as the black body will be a surface emitter, therefore will not show exact black body spectra, that sound right?
 
  • #4
You should reference your statements.
Other wise, answers become off track quite easily.

A mechanism of light emission from a single bubble sonoluminescence (SBSL) was formulated by assuming that the source for the light emission is bremsstrahlung in partially ionized gases. This emission mechanism turns out to be same as the black body radiation with finite absorption, which confirms that the principal mechanism of SBSL is bremsstrahlung with slight black body emission nature. Also the spectrum was measured and the observed results were compared with the calculated ones. Calculated and experimental results yield common spectral behavior in the visible region: the spectral radiance shows power-law dependence on wavelength with an exponent of -2.5. The SBSL spectrum which is characterized by the continuous one with no major peaks has been confirmed experimentally. The bubble dynamics model proposed also takes account the afterpulse characteristics of SBSL.
http://journals.jps.jp/doi/abs/10.1143/JPSJ.69.112

I outlined the statement in red.
Is that what you are referrring to?

also it occurs to me that a plasma will be a VOLUME emitter, where as the black body will be a surface emitter, therefore will not show exact black body spectra, that sound right?

That should depend upon the density of the plasma, no?

which makes very little sense to me, how can something be bremsstrahlung AND black body?
The species within the plasma do not share only one specific kinetic energy, ie velocity, but have a range from 0 to some high number. Probably a distribution with something to do with a famous physicist, maybe Boltzman, not sure, depending upon the temperature. With a great number of interactions, at different velocities, the EM approaches thermal or blackbody.

Having said that, though, the spectrum from a mercury gas lamp, or neon sign shows a line spectrum, or close to it, since some of the species are interacting. Here the emmission, absorption of electrons is responsible for the majority of electromagnetic radiation, and this plasma does not show blackbody.

Not an expert in the subject, but hpefully this will spur some discussion.
 
  • #5
256bits said:
You should reference your statements.
Other wise, answers become off track quite easily.http://journals.jps.jp/doi/abs/10.1143/JPSJ.69.112

I outlined the statement in red.
Is that what you are referrring to?

Yes that's the one, and ok will do, thanks.
256bits said:
That should depend upon the density of the plasma, no?

Yes, this did occur to me, for if you imagine a very dense plasma the 'internal' ion emission will only meet the outer and inner ions, it will be the outer ion emission that is observed outside the plasma. (assuming spherical confinement).

So for a very dense plasma the spectra will be extremely close to BB radiation spectra, from only the surface ions, is that what you believe the paper is referring to when it says "bremsstrahlung with slight black body emission"?

I don't understand the term "finite absorption", if it was a BB then it would not be finite, so I'm unsure how they can classify it as such. Is it a way of saying 'almost' BB radiation like?
256bits said:
The species within the plasma do not share only one specific kinetic energy, ie velocity, but have a range from 0 to some high number. Probably a distribution with something to do with a famous physicist, maybe Boltzman, not sure, depending upon the temperature. With a great number of interactions, at different velocities, the EM approaches thermal or blackbody.

Having said that, though, the spectrum from a mercury gas lamp, or neon sign shows a line spectrum, or close to it, since some of the species are interacting. Here the emmission, absorption of electrons is responsible for the majority of electromagnetic radiation, and this plasma does not show blackbody.

Not an expert in the subject, but hpefully this will spur some discussion.

I think I see where the paper is going, that it is bremsstrahlung in nature but tends towards the characteristics of a BB, would that be a correct interpretation?

Thanks very much for the reply, very helpful!
 
  • #6
Update, during my research found an interesting statement which I think helps:


(from VOLUME 88, NUMBER 19 PHYSICAL REVIEW LETTERS 13 MAY 2002)

This could happen because the observation of a spectrum which accurately matches a blackbody does not absolutely require that the conditions generating the blackbody be the same as those invoked in the traditional derivation of an equilibrium blackbody source. .

And leads onto (SBSL)

In this case insight into the light-emitting mechanism cannot be obtained without additional information. On the other hand, if the blackbody spectrum is actually produced by
conditions that match the traditional conditions (matterlight equilibrium, and a high density of states, then the observation of an SL blackbody spectrum leads to interesting
consequences regarding the bubble’s interior.

SO it says something of the design of a BB emitter, that it may not necessarily be a BB emitter in the traditional sense.
 
  • #7
I found this topic is related to my question and hope someone give me feedback.

My question is regarding continuous spectra in laser-induced breakdown. There are many figures have shown atomic spectra lines (spikes) on top of the continuous spectra at early stage of laser-inducded breakdown (e.g., figure 2 and 3 in http://www.opticsinfobase.org/ao/abstract.cfm?uri=ao-49-13-C80). I am wondering whether the idea of blackbody radiation still applicable for this case.

Then my questions is:
Can we determine the gas temperature using blackbody (Planck's law) although there are continuous spectra with atomic spectra lines?
 

1. Can a plasma give off black body emission?

Yes, a plasma can give off black body emission. Black body radiation is a form of electromagnetic radiation emitted by any object with a temperature above absolute zero. As plasmas can reach extremely high temperatures, they can emit black body radiation.

2. What is black body emission?

Black body emission is the electromagnetic radiation emitted by an object with a temperature above absolute zero. It is characterized by a continuous spectrum and the intensity of the radiation is dependent on the temperature of the object.

3. How is black body emission related to plasma?

As plasmas can reach extremely high temperatures, they can emit black body radiation. This is because the particles in a plasma, such as ions and electrons, have a high amount of kinetic energy, which manifests as heat and the emission of electromagnetic radiation.

4. Is black body emission the same as thermal radiation?

Yes, black body emission and thermal radiation are often used interchangeably. Both terms refer to the same phenomenon of electromagnetic radiation emitted by an object with a temperature above absolute zero.

5. Are there any applications of black body emission from plasmas?

Yes, there are several applications of black body emission from plasmas. Some examples include plasma lamps, which use black body radiation to produce light, and solar simulators, which use plasmas to simulate the black body radiation of the sun for testing solar panels.

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