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1answer
11 views

Photoemission to measure band gaps?

Photoemission works by conservation of energy: $$\bar{h}\omega = E_{kin} + E_i + \phi$$, where $\bar{h}\omega$ is the incident photon, $E_{kin}$ is the measured kinetic energy of the ejected ...
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0answers
18 views

What is the physical cause of the EMF emissions / behavior of light/ photons? [closed]

I came across an interesting representation of a photon that explains its EMF behavior- https://YouTu.be/MH6XDiTt6xY which firmly puts photons as a particle with negligible rest mass and inertia. That ...
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0answers
17 views

GEN3's 10nm-30nm Contiuum Radiation Measurements

What is the most likely explanation for the 10nm-30nm continuum radiation reported in "Validation of the Observation of Soft X-ray Continuum Radiation from Low-Energy Pinch Discharges in the Presence ...
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0answers
28 views

Which Hydrogen Emission Lines Appear First?

When a blackbody is heated, it radiates photons. At low temperatures, there isn't much radiation at high-energy end of the spectrum but as the temperature raises, high-energy radiation becomes ...
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0answers
49 views

Calculating Natural Broadening of Emission Lines

I'm trying to demonstrate the small effect of Natural Broadening as compared to other types of broadening (Doppler, Stark, van der Waals, etc.) and my calculations don't match the accepted values. My ...
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2answers
31 views

Photoelectric effect and wave particle duality

In a vacuum, if electrons are accelerated by a certain voltage, giving the electrons a specific de Broglie wavelength and were incident on a piece of metal, providing the wavelength was roughly the ...
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0answers
35 views

Can a simple harmonic oscillator describe Rabi oscillations?

I've been trying to simulate a resonant laser oscillation of a two level atom with Rabi frequency $\Omega$ and a rate of spontaneous emission $\Gamma$. So the wavefunction would be $\mid \Psi\rangle = ...
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2answers
54 views

Probability of photon to photon collision

2 photons having sufficient energy can collide and form an electron positron pair (which then annihilate and form a new photon pair - with lower energy?). I assume this means that they can't collide ...
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0answers
22 views

Do silver or gold nano-partcles possess fluorescence?

my question is not only about silver or gold but any other metal nano-particles. Anyway, I'm personally interested in silver. So why do the tiny clusters (several atoms) of silver and gold possess ...
0
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1answer
41 views

What's the difference between stimulated and spontaneous emission in lasers and diodes?

I know that an LED emits light by spontaneous emission. To get more coherent and Monochromatic light, we should use a laser. What is the reason that laser light is the most coherent and ...
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0answers
32 views

Photon spin and photo electric effect

If a photon with spin angular momentum $+1$ with sufficient energy strikes an electron with spin $+1/2$, emission will take place. As angular momentum can't be conserved, what will happen?
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1answer
33 views

Electron and photon relation [duplicate]

While a photon is mass less but when it converts to an electron how mass can come into being ?
5
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2answers
65 views

Why absorption spectum is not identical to emission spectrum?

Hydrogen emission and absorption spectral lines are typically depicted as the same: (source) However, in more complex systems, the emission and absorption spectra are significantly different. For ...
2
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1answer
54 views

LASERS: How do we get all the emitted photons of equal wavelength & equal phase? [duplicate]

As far as the working of lasers is concerned, I was convinced till the part that the light flashes on a ruby stone and the electrons are excited and then again go back to their ground state and then ...
3
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1answer
75 views

How many photons are there in free space on average

Estimates of the amount of for example "dark matter" are of interest to the cosmologists. However, I have never seen an estimate of how many "free" photons could be speeding about in the known ...
2
votes
1answer
68 views

Can an absorbed photon be emitted as two photons?

I am taking an intro to astronomy class, and have touched upon absorption and emission lines and etc, the prof asked this question in class and got me thinking. I would want to say no, because one ...
2
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0answers
65 views

Estimating temperature with Boltzmann relation with split emission lines

I'm trying to estimate the temperature of a plasma through the use of hydrogen lines, $H_{\alpha}$ and $H_{\beta}$ using the Boltzmann relation: $$ \frac{ n_{2} }{ n_{1} } = \frac{ g_{2} }{ g_{1} ...
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0answers
32 views

Emission of photon in space [duplicate]

A source is emitting photons towards all directions. An observer sitting at millions of light years away can receive the photon from all the places. There will be infinite directions from where the ...
0
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0answers
45 views

What are the properties of the electromagnetic radiation from a magnetron?

There are different modes of EM radiation. A bulb emits photons in a wide range of wavelengths and without polarisation. Radio waves are polarized modulated radiation. What is about the radiation ...
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2answers
43 views

How does different particle size account for different colors?

I understand how objects have color in terms of absorption and reflection; however, in stained glass, various nano-particles can have different colors depending on the particle size. As described in ...
1
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1answer
33 views

Mossbauer effect - Deriving the recoil energy formula

I am working on a problem that deals with the Mossbauer effect and calculating the recoil energy on a iron-57 atom, initially at rest and excited to 14.4 keV, after it emits a photon. In the Wikipedia ...
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1answer
47 views

Bandgaps of Silicon and their application in active optical elements

I know that silion has an indirect bandgap at $E = 1.12 \, eV $ or $ \lambda = 1.107 \, \mu m$ and I have read that active optical processes like absorption and emission have a decreased likelihood to ...
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0answers
23 views

What does “at%” refer to in sol-gel method?

I'm reading on the preparation of ZnO thin films for UV stimulated emission and I found a method called Sol-Gel. During this I found a paragraph saying, " the ratio Ag/Zn in the sol is 3 at%......". ...
0
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1answer
30 views

When light is reflected, if some of the light is absorbed in the particle, does it change the particle?

Which color/frequency of the light is absorbed and which part is reflected? How is it determined which part will be absorbed? Does that depend on the particle? N.B: When I say particle, please keep ...
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2answers
288 views

Atomic natural line width

In laser cooling, with a model of a 2-level atomic system, spontaneous emission is stated to be dependent on the "natural line width" of the excited state of the atom. This width is defined as the ...
2
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2answers
72 views

During the “Dark Ages” of the Universe's evolution, how lumpy (anisotropic) and dynamic was the mass distribution?

In the dark ages between recombination (~0.4 Myr post-BB) and reionization (~300 Myr post-BB) of atoms, there was not any condensed-phase matter (except maybe some form of dark matter), nor radiation ...
2
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1answer
83 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
151 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
49 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
114 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
42 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 ...
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4answers
2k views

Spectral line formula [closed]

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 is =$ \frac{2(n-1)}{2}$ is this right or is there ...
2
votes
1answer
121 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
69 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
71 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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2answers
48 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
462 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
215 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?
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1answer
620 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 ...
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3answers
321 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
votes
1answer
92 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
votes
1answer
64 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
51 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
384 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 ...
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0answers
259 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 ...
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0answers
74 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
63 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 ...
6
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3answers
393 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
113 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
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3answers
128 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 ...