Why Do We Have The Effect Of Spontaneous Emission And Absorption

In summary, the conversation discussed a question related to the interaction with the Quantum EM Field on a stationary state, and the answer was given using Fermi's Golden Rule. The conversation also mentioned a paper on the topic, which can be found on Wikipedia, and suggested further reading for those interested in physics and QFT. The conversation ended with a recommendation to avoid studying Zee.
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bhobba
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Hi All

In another thread I answered was a question related to this and noticed another as well, so I thought I would give the full answer in its own thread rather than write it out twice. The other question has been deleted but here is the full detail anyway.

First see:
http://www.physics.usu.edu/torre/3700_Spring_2015/What_is_a_photon.pdf

We can view the interaction with the Quantum EM Field on an otherwise stationary state as a small perturbation and hence apply an important theorem - Fermi's Golden Rule:
https://en.wikipedia.org/wiki/Fermi's_golden_rule

I gave a link to Wikipedia, but that's just because it came up first on a search to get a link. There are tons of other papers on it, and while fully working through it may take a bit of time if you have not seen it before, it is an important result, and worth the effort in understanding it.

Thanks
Bill
 
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... so, in other words, "how would a stationary state change?" ... with the answer being, it does not: the physical state in real life is not absolutely the stationary one because the calculation left out some stuff.
Only going into detail.

Have I got it?

It's neat. Could it be an insights article?
 
  • #3
Simon Bridge said:
Have I got it?

You got it.

That paper is an insights article itself without me or someone else writing one.

Watch out if you are carefully going through the math - I can't remember where but there is an 'error' I had to use some other books like Dirac's classic text to clarify. But if you come across it just do a post here.

Excellent introduction to QFT as well - read before studying QFT for the Gifted Amateur and Student Friendly QFT. Both books are more than good enough to have as an introduction all those seriously interested in physics should have about QFT. Beyond that I would study Banks:
https://www.amazon.com/dp/0521850827/?tag=pfamazon01-20

As one review says - perfect to read before going onto the master - Wienberg.

Do not study Zee - I originally thought it good - but now think its far too 'pokey' and do not like it.

Thanks
Bill
 

1. Why do we observe spontaneous emission and absorption of light?

Spontaneous emission and absorption occur due to the intrinsic properties of atoms and molecules. When an atom or molecule is excited, it can release energy in the form of photons, resulting in spontaneous emission. Similarly, when a photon interacts with an atom or molecule, it can be absorbed, causing an energy transition within the atom or molecule.

2. What causes spontaneous emission and absorption?

Spontaneous emission and absorption are caused by the quantum nature of matter. According to quantum mechanics, atoms and molecules can exist in discrete energy levels. When an atom or molecule is excited, it can spontaneously transition to a lower energy level, releasing a photon. Similarly, when a photon interacts with an atom or molecule, it can cause an energy transition within the atom or molecule, resulting in absorption.

3. How does spontaneous emission and absorption affect the behavior of light?

Spontaneous emission and absorption play a crucial role in the behavior of light. They determine the intensity, direction, and polarization of light. The absorption of light by atoms and molecules is responsible for the colors we see, while spontaneous emission is essential for the production of light sources such as lasers.

4. Can we control spontaneous emission and absorption?

While spontaneous emission and absorption are natural phenomena, scientists have found ways to control and manipulate them. For example, by using external stimuli such as electric or magnetic fields, we can influence the energy levels of atoms and molecules, thus controlling their absorption and emission properties.

5. How do spontaneous emission and absorption contribute to technological advancements?

Spontaneous emission and absorption are crucial for various technological applications. They are the basis for many devices, such as lasers, LEDs, and solar cells. These technologies rely on the controlled emission and absorption of light to function, making them essential for modern society.

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