Why Do We Have The Effect Of Spontaneous Emission And Absorption

[bhobba]

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

 

[Simon Bridge]

... 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?

 

[bhobba]

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