I have learned that Einstein predicted that it was possible to stimulate and excited atom with an incoming photon, and that the atom would have a high probability of emitting a similar photon having same frequency, phase and direction.

(Of course, the incoming photon should match the excited state so as to facilitate an emission in the first place.)

 

My questions are these.

 

How the hell was Einstein able to predict that this phenomenon would occur?

As I understand it, no experiment had been done prior to this prediction.

 

Is the probability binary, such that it either emits a similar photon or none at all? Or can it emit a "random" photon, or does stimulated emission overrule spontaneous emission?

The answer is:

 

Maths.

 

He made some basic assumptions and applied some physical laws and that was the conclusion, when I get a chance and am awake (a couple of days) I'll try and look up the paper to explain it more rigorously that this rather vague comment

Greatly appreciated!

 

Is the original paper available on the net?

Here's a summary

http://www.phytem.ens-cachan.fr/telechargement/Optique_Quantique/Kleppner_Coef_Einstein.pdf

 

The original papers were in German

 

Strahlungs-Emission und Absorption nach der Quantentheorie (1916)

http://nausikaa2.rz-berlin.mpg.de/digitallibrary/digilib.jsp?fn=permanent/einstein/cw/081_1916/pageimg/&pn=3&ws=1.5

 

Zur Quantentheorie der Strahlung (1917)

http://www.ecse.rpi.edu/~schubert/More-reprints/1917%20Einstein%20(Physikalische%20Zeitschrift)%20Zur%20Quantentheorie%20der%20Strahlung.pdf

Here's a summary

http://www.phytem.ens-cachan.fr/telechargement/Optique_Quantique/Kleppner_Coef_Einstein.pdf

 

...

 

Have to say I did enjoy that 2005 Kleppner article in Physics Today. Thanks for posting the link. It looks like the French site scanned it (for educational purposes) making it more accessible than it would be in the Physics Today archives. Don't know that for sure since I didn't try the PT archive. In any case it's a goodie.

 

I always forget how mysterious AE's mind is. And then I accidentally re-encounter it an article like this and am surprised once again. Like a sleepwalker strolling along the top of a fence

I have learned that Einstein predicted that it was possible to stimulate and excited atom with an incoming photon, and that the atom would have a high probability of emitting a similar photon having same frequency, phase and direction.

As I recall he used arguements from thermodynamics. If you do a search under "Einstein's A and B coefficients," "stimulated emission" and thermodynamics then you might find what you're looking for. If not then let me know and I'll did through the texts that I have and see if I can find a good explanation/derivation. If you'd like I can then scan the pages in and upload it onto my website where you can download them for your reading pleasure.

 

However swansont's link seems pretty good. Excellant link swansont!!

He made some basic assumptions and applied some physical laws and that was the conclusion' date='..

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Ummm ... that's true of all Einstein's discoveries. In fact usually true for discoveries in general.

 

Pete

Edited August 25, 200817 yr by Pete

Ummm ... that's true of all Einstein's discoveries. In fact usually true for discoveries in general.

 

Pete

 

Yes, interesting that isn't it... Lots of people miss that though when talking about science.