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2
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1answer
34 views

Why is stimulated emission necessary for detailed balance?

Detailed balance says that in equilibrium, the total number of particles leaving a certain quantum state per unit time equals the particles arriving in that state per unit time. Now, without the ...
1
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1answer
54 views

How did Einstein know that it was necessary to include “stimulated emission”?

How did Einstein know that it was necessary to include "stimulated emission" which was in the same direction as the incident photon and in phase with it?
0
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1answer
40 views

What is supposed to be used as $m$ in $m\lambda = d\sin \theta $

I know that $m$ is the "order number", but I don't understand how this applies to the lab we did. We looked at Hydrogen gas through a diffraction grating (500 lines/cm or something like that) and saw ...
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0answers
44 views

Why wouldn't any Emission Theory work?

http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/origins_pathway/#Emission Here, at the Emission theories of light, I loved the discussed theory. There seems to be a contradiction right ...
0
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1answer
29 views

Semiconductors light emission

Suppose a pure semiconductor, with a direct gap. If I apply a constant voltage to it the electrons will jump to the conduction band. So when I turn it off will it emite light?, because the electrons ...
0
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3answers
146 views

Spectral line formula

Two years back my friend told me a simple formula for calculating the number of spectral lines. But, now I'm a bit confused about it number of lines in= 2(n-1)/2 is this right or is there any error ...
2
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1answer
70 views

Probability of photon emission

If a photon of a given wavelength is absorbed by an electron (for simplicity, let's assume the electron has only one excited state), does the probability that the electron jumps to its excited state ...
0
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2answers
56 views

Is shape of a black body much of a concern in physics?

When I read a book on computer vision, I stumble upon the ideal black body model. Using Lambert's cosine law (wiki), one is able to compute the intensity of an area element dA w.r.t. some observer. ...
1
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1answer
62 views

Spectral lines and QM

In the various presentations I've seen so far in atomic physics of series such as the Balmer series, the wavelength of each spectral line is definite - but in QM, free particles have no definite ...
2
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1answer
28 views

Can a fluorophore emit a higher energy photon than it absorbed

It is unclear for me what processes are exactly in place during the absorption-reemission process of a fluorescing photon. I am thinking about the case when the absorption and emission spectrum ...
1
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1answer
106 views

Work function definition

As in this post How would I calculate the work function of a metal, the definition is given by "the minimum thermodynamic work (i.e. energy) needed to remove an electron from a solid to a point in the ...
0
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1answer
94 views

One photon and two electrons

Since an absorption of one photon by two electrons was experimentally noticed when one photon excites two atoms in touch, should we accept even an emission in common of one photon by two electrons?
3
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1answer
184 views

In how many possible ways can a photon be emitted?

I am currently studying atomic physics, and I encountered the question above. I am posting this question because I can't afford to move on with even the tiniest bit of uncertainty in my understanding ...
14
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3answers
260 views

Does the diffracted electron radiate photons?

When electron is diffracted after the slit it might follow different direction, than before the slit. That means, that going through the slit it gains some acceleration. And accelerated charge emits ...
0
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0answers
11 views

High photon flux for ultrashort photons?

What is currently the highest photon flux one can achieve for single photons with a coherence length of femtoseconds? Does some know roughly know the order of magnitude? Unfortunately I was not very ...
0
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0answers
83 views

Spontaneous de-excitation of an atom

Consider the Hamiltonian for the process of spontaneous de-excitation on an excited atom, (an electron jumped to a higher energy level while a lower energy level is not complete). This Hamiltonian ...
0
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1answer
52 views

photon absorption and emission

I was reading a book (Sears Zemansky) about this subject but I didn't understand something of an example, and this is that according to me there should be a process of emission for each of absorption ...
0
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0answers
46 views

QED: what is the relationship between emission and absorbtion spectrums? (and why do plants absorb blue light and emit green light..)

I'm interested in this because of photosynthesis, but hte question is general. I'm looking for a QED explanation. A lot of the explanations talk about light shining on a plant getting aborbed, ...
0
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1answer
41 views

What is “Lifetime Intensity” in photoluminescence?

I'm reading an article "Surface plasmon enhanced Förster resonance energy transfer between the CdTe quantum dots". Link The reasearchers are writing about increase in "lifetime intensity" and even ...
0
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0answers
42 views

When optically pumping a lasing gain medium with another laser, does Stimulated, or Spontaneous emission dominate?

Much of my reading seems to indicate that laser pumping results in a fluorescent stokes shift but somehow photon vector is maintained. I've seen the phrase "Spontaneous Fluorescence by Stimulated ...
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3answers
135 views

Do electrons in absorption spectra absorb photons with enough energy to release them from their parent atoms?

Absorption spectrum theory says that electrons in the atoms absorb only photons of certain frequencies, which causes the dark lines in an absorption spectra. However, I understand that electrons that ...
7
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0answers
240 views

Integration & bremsstrahlung calculation

In this paper (relevant pdf section) that I'm reading, involving the calculation of bremsstrahlung in electron proton scattering (diagram below), the author calculates the integral over outgoing ...
1
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0answers
50 views

Spontaneous parametric down conversion and relative time of emission of two entangled photons

A pump beam excites a non-linear crystal which produces two entangled photons with perpendicular polarization, namely in the state $|HV>+|VH>$. Are there examples where one of the photons was ...
2
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0answers
43 views

How does a photon travel through an electron cloud?

We all know that the exact position and exact velocity of an electron in an atom cannot be determined simultaneously, as per the Heisenberg uncertainty principle. We only talk about the probability of ...
5
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3answers
243 views

What if all the electrons leave a metal?

I was studying photoelectric effect. Then I thought that what will happen if all the electrons from a metal piece come out as photoelectrons by using a light source of particular frequency? Will the ...
3
votes
1answer
66 views

What is the frequency of a photon emitted by an accelerated charged particle?

When a charged particle is accelerated by a field, it would seem there are many possible photons that could be emitted to obey conservation of momentum. Is it random, or time-dependent, or based on ...
2
votes
3answers
114 views

Photon speed going from $0$ to $c$ initially? [duplicate]

I have read many questions which ask whether there can be photons at speed other than the speed of light and all of them are answered no! But when the photon is created for ex during electron ...
3
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3answers
178 views

Stimulated emission and No cloning theorem

I have a little trouble with the simulated emission. I know of the no-cloning theorem which states that it is not possible to duplicate any state. One the other hand, I know about the stimulated ...
3
votes
1answer
87 views

Using the fine structure constant to measure atomic and molecular sizes

This is kind of a coursework question but it bring up some really interesting things about the fine structure constant $\alpha$ so I wanted to post it to not only make sure I understood something but ...
2
votes
0answers
162 views

Why does Pyrex glow orange under UV?

In a Physics lesson today our teacher performed a demonstration to show how quinine in tonic water glows blue when under UV light. He showed us the same demonstration using water in a Pyrex beaker, ...
3
votes
2answers
65 views

How do molecules bubble off a photon?

After being excited by a photon, an electron of a photoactive molecule jumps to a higher electronic state. When it relaxes, the molecule emits a photon (in simple terms). How is this photon ...
5
votes
3answers
386 views

Acceleration of electric charges and radiation

According to classical electromagnetic theory, accelerated charges should emit radiation and lose energy. The reason given in my book why atoms don't emit radiation (say, when the atom moves along a ...
1
vote
1answer
41 views

Excited Energy levels of Hydrogen vs Solids

My question has to do with Excited Energy Levels. I keep reading and learning that all objects/most solids emit infrared radiation. But to emit radiation, an object's particles must first enter a ...
0
votes
1answer
70 views

Does firing electrons at an object change its colour?

If one had an electron gun capable of firing electrons with a specific energy at an object, can it change its colour? I think it is possible because the emission spectrum of the material would ...
1
vote
1answer
52 views

Visible Lines for Hydrogen

Say H atoms are excited to 4th level, n=4 that is, how many lines do we see? How to decide the number of the lines?
1
vote
1answer
493 views

Calculating laser wavelength/power to cause emission of light in a gas?

I've become interested in volumetric displays. In particular I'm looking at a pair of lasers scanning a volume of gas such that the intersection of the lasers would supply enough energy to cause the ...