Can stimulated emissions from CO2 be absorbed?

In summary: Infrared radiometry can be done from space, too.In summary, when an excited molecule absorbs a photon, it will emit two coherent photons if it is hit by a second photon of the same frequency. However, this does not always happen as the molecule can also relax back to its ground state through spontaneous emission. The absorption and emission of coherent photons can be affected by various factors, such as the material of the object being hit and the direction of travel of the photons. Additionally, while CO2 can absorb photons, it is not typically used as a laser medium due to low quantum efficiency.
  • #1
Alastair McD
15
1

When an excited molecule absorbs a photon two coherent photons are emitted. If one of these photons is absorbed by a second molecule, since the emission was coherent then that molecule will absorb the second photon too. If the second molecule was in the ground state then it will become excited by the absorption of the first molecule. Will the second photon be absorbed too, and cause two coherent photons to be emitted, with the result that there in no net absorption?
 
Physics news on Phys.org
  • #2
Alastair McD said:
If one of these photons is absorbed by a second molecule, since the emission was coherent then that molecule will absorb the second photon too.
Why should it?
 
  • #3
Since they are coherent both are traveling together in the same direction, if one hits a molecule so will the second.
 
  • #4
Photons are not billard balls. They do not "hit" molecules.

Can you stop light from a laser pointer with a sheet of paper, your hand and other things? There is your (incoherent) absorption of coherent light.
 
  • #5
mfb said:
Photons are not billard balls. They do not "hit" molecules.

Can you stop light from a laser pointer with a sheet of paper, your hand and other things? There is your (incoherent) absorption of coherent light.

Paper, human hands, and other thing are not made of carbon dioxide and so do not emit stimulated radiation.
 
  • #6
Alastair McD said:

When an excited molecule absorbs a photon two coherent photons are emitted.
In general, no.
If one of these photons is absorbed by a second molecule, since the emission was coherent then that molecule will absorb the second photon too.
No.

What phenomenon are you trying to open for discourse here? You have to be more specific if you hope for any meaningful replies.
 
  • #7
Alastair McD said:
Paper, human hands, and other thing are not made of carbon dioxide and so do not emit stimulated radiation.
They do not emit it, but they can absorb it.
Anyway, CO2 can absorb it as well. It absorbs a photon, done. It can re-emit the photon later, either spontaneous (in a random direction) or stimulated (if the laser is still switched on). Alternatively, it can lose the energy in non-radiative ways.
 
  • #8
Heinera and mfb,

Thank you for your replies. It seems that I have not explained my dilemma fully. I will try again.

When a greenhouse gas molecule absorbs a photon, the molecule becomes excited. If the molecule is hit by a second photon of the same frequency, before it has relaxed back to the ground state (by spontaneous emission), then it will emit an additional photon by stimulated emission with the "identical phase, frequency, poalisation, and direction of travel as the [incident] photon" https://en.wikipedia.org/wiki/Stimulated_emission

Perhaps I should have writtem "When an excited molecule is hit by a photon the result is two coherent photons are produced." It seems to me that it would be imposible for that coherent pair of photons to be absorbed by a molecule in the ground state since the first photon would excite the molecule and the second produce a stimulated emission.

I was hoping that I would find an expert here who could confirm my thinking, or expain to me why I am wrong citing experimental evidence. I believe that the distance of the Moon is measured using a CO2 laser, so the beams to and from the Moon cannot be significantly absorbed by the CO2 in the Earth's atmophere.
 
  • #9
Alastair McD said:
When a greenhouse gas molecule absorbs a photon, the molecule becomes excited. If the molecule is hit by a second photon of the same frequency, before it has relaxed back to the ground state (by spontaneous emission), then it will emit an additional photon by stimulated emission with the "identical phase, frequency, poalisation, and direction of travel as the [incident] photon" https://en.wikipedia.org/wiki/Stimulated_emission
It can do so, it does not have to.
Alastair McD said:
I was hoping that I would find an expert here who could confirm my thinking, or expain to me why I am wrong citing experimental evidence. I believe that the distance of the Moon is measured using a CO2 laser, so the beams to and from the Moon cannot be significantly absorbed by the CO2 in the Earth's atmophere.
I don't think CO2 lasers are used, as the detection needs a good quantum efficiency and CO2 lasers emit at ~10 micrometers, too low-energetic for sensitive detectors. Wettzell uses Nd:YAG in the near infrared (~1 micrometer), not sure about the others.

The transmittance at 10 micrometers would be about 80%, see https://upload.wikimedia.org/wikipedia/commons/e/e9/Atmospheric.transmittance.IR.jpg. The presence of CO2 gives a small dip in the spectrum, so exactly at the lasing frequency transmission might be lower.
 

Related to Can stimulated emissions from CO2 be absorbed?

1. Can stimulated emissions from CO2 be absorbed?

Yes, stimulated emissions from CO2 can be absorbed. In fact, this is how lasers work - by stimulating the emission of photons from CO2 molecules and then amplifying and directing the resulting beam of light.

2. How does stimulated emission from CO2 contribute to climate change?

Stimulated emissions from CO2 contribute to climate change by trapping heat in the Earth's atmosphere. When sunlight reaches the Earth's surface, some of it is absorbed and some of it is reflected back into space. CO2 molecules in the atmosphere absorb some of this reflected heat and re-emit it in all directions, including back towards the Earth's surface. This is known as the greenhouse effect and is a major contributor to global warming.

3. Can stimulated emissions from CO2 be controlled or reduced?

Yes, stimulated emissions from CO2 can be controlled and reduced through various methods. One way is to reduce the amount of CO2 being emitted into the atmosphere, such as through reducing the burning of fossil fuels. Another way is to promote the absorption of CO2 through natural processes, such as reforestation or the use of carbon capture and storage technology.

4. Are stimulated emissions from CO2 harmful to human health?

Stimulated emissions from CO2 are not directly harmful to human health. However, as mentioned earlier, they contribute to climate change which can have negative impacts on human health. For example, extreme weather events, changes in air quality, and the spread of vector-borne diseases are all consequences of climate change that can directly affect human health.

5. Is there any controversy surrounding stimulated emissions from CO2?

Yes, there is some controversy surrounding stimulated emissions from CO2. While it is a well-established scientific concept, there is debate over the extent to which human activities, such as burning fossil fuels, are contributing to the increase in atmospheric CO2 levels and the resulting effects on climate change. There are also differing opinions on the best ways to reduce and control CO2 emissions.

Similar threads

I Qualitative description of stimulated emission & population inversion
    • Quantum Physics
Replies
18
Views
1K
A Increase of coherent length in stimulated emission
    • Quantum Physics
Replies
19
Views
2K
I Two-photon Stimulated Raman Transitions
    • Quantum Physics
Replies
2
Views
847
I What's the interval between photons in stimulated emission?
    • Quantum Physics
Replies
2
Views
1K
I Mach-Zehnder with Stimulated Emission
    • Quantum Physics
Replies
1
Views
717
I How can a photon "stimulate emission" if it really does (Einstein coefficients)
    • Quantum Physics
Replies
11
Views
1K
I Stimulated Emission & Emitted photon direction
    • Optics
Replies
1
Views
1K
I Questions about Franck-Condon principle
    • Quantum Physics
Replies
3
Views
2K
I Are all processes CPT symmetric like measurement, stimulated emission?
    • Quantum Physics
Replies
8
Views
853
B What is the fundamental principle behind the operation of a laser?
    • Quantum Physics
Replies
9
Views
1K

Hot Threads

Recent Insights

Back
Top