Can a Black Body Emit Only One Photon After Being Hit By a Single Photon?

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Discussion Overview

The discussion centers around the behavior of a black body when it absorbs a single photon, particularly at very low temperatures, and the implications for the emitted spectrum. Participants explore the relationship between the absorbed photon and the resulting emission spectrum, questioning how the characteristics of the emitted photons relate to the initial conditions and properties of the black body.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that a black body at 0K would absorb a photon and emit a continuum spectrum, raising questions about the nature of this emission and its dependence on the wavelength of the absorbed photon.
  • Another participant argues that the black-body spectrum is a statistical effect and that the behavior of a single photon requires a solid state analysis.
  • There is a discussion about whether an ideal black body can emit a continuum spectrum even when starting at absolute zero, with some participants questioning the implications of temperature changes due to photon absorption.
  • One participant notes that the emitted spectrum would depend on the temperature increase from the absorbed photon, suggesting the use of Stefan-Boltzmann's law to calculate this temperature change.
  • Another participant expresses uncertainty about the exact behavior of a perfect black body after absorbing a photon, proposing that it may not produce a continuum emission and could instead re-emit a photon of the same wavelength.
  • There is speculation about the probabilistic nature of photon emission and how it might relate to the black body intensity distribution.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the behavior of the black body after absorbing a single photon. Multiple competing views are presented regarding the nature of the emitted spectrum and the role of temperature.

Contextual Notes

The discussion highlights limitations in understanding the transition from a single photon interaction to the resulting emission spectrum, particularly in terms of temperature dependence and statistical effects. There are unresolved questions about the specific formulas and models applicable in this scenario.

fluidistic
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To make my question simpler, assume that there's a black body at 0K or very close to it (if we can't assume there's a body at 0K).
Say I have a monochromatic source of photons which sends 1 photon on the black body. The wavelength of the photon is 500 nm so around green. If I understood well how a black body behaves, it will absorb the photon and re-emit a continuum spectra of light. In other words, it will radiate an infinity of photons. Obviously the black body can't emit another 500 nm photon otherwise it would emit only 1 photon (due to conservation of energy) and not a continuum spectra. I realize that in a realistic case the black body cannot emits an infinity of photons, but it doesn't matter for my question.
How can I know what will be the spectra of a black body, knowing that I send a photon of wavelength \lambda?
So after all, the "continuum spectra" can be very limited in wavelength range? I'm interested in knowing how to determine for example what would be the most energetic photon that will be emitted in my previous example.
By the way it's not a homework question so any reply of the form "look at Planck's Law" or any other Law satisfies me. Explanations are welcome too.
 
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The black-body spectrum is a statistical effect which only corresponds to average properties. What happens to a single photon requires a solid state analysis.
 
zhermes said:
The black-body spectrum is a statistical effect which only corresponds to average properties. What happens to a single photon requires a solid state analysis.

Hmm interesting. Even in an idealization of a black body? I.e. absorbs all incident light and re-emits a continuum spectra.
 
The continuum spectrum it emits will be exclusively dependent on its temperature. So, that depends on how much it heats up due to the single incident photon. If it were to remain at 0K, it would not emit any spectrum at all.
 
cjl said:
The continuum spectrum it emits will be exclusively dependent on its temperature. So, that depends on how much it heats up due to the single incident photon. If it were to remain at 0K, it would not emit any spectrum at all.

Ok I see. It can't remain at 0K (it's not infinite in size) since it absorbs a photon. I think I could use Stefan-Boltzmann's law to calculate the gain of temperature due to the absorption of 1 photon. Say it gives me it heats up to 0.1K. What formula can I use to see the black body radiation at this temperature?
I'm really curious if there's at least 1 photon with a close to 500 nm wavelength. It's almost impossible.
 
fluidistic said:
Hmm interesting. Even in an idealization of a black body? I.e. absorbs all incident light and re-emits a continuum spectra.
The reason why a black-body behaves the way it does is because of statistics and averaged quantities. It was all of the Boltzmann distribution, einstein's quantization that pieced it together.

I don't know exactly what a perfect black-body, starting in the ground state, would do after being hit by a single photon... but its definitely not going to produce black-body, continuum emission. Whatever results will most likely be purely quantum mechanical... maybe just re-emit a photon with the same wavelength? More likely a probabilistic function would decrease the probability of producing some combination of 'n' photons, and whatever combinations of frequencies (the sum of which equal the initial frequency)? Anyone out there have specifics?

EDIT: another guess, the blackbody intensity distribution might describe the probability with which a photon, of energy less than or equal to that available, is emitted.
 

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