Questions tagged [photon-emission]
This tag is for questions regarding to Photon Emission. Photons are emitted by the action of charged particles, mainly due to making a transition from a high energy state to a lower energy state. Although they can be emitted by other methods including radioactive decay.
316
questions
-1
votes
0
answers
26
views
Accurately turning spectral lines of elements into audio [closed]
This video uses the sum of the sin waves of the Lynman and Balmer series to obtain the "audio" of Hydrogen. To get a more accurate representation, should all the sin waves of hydrogen ...
2
votes
1
answer
93
views
How many cavity round trips typically occur inside laser resonators?
Is it possible to estimate the number of cavity round trips occurring inside typical laser resonators, e.g. in a laser diode or a He-Ne laser?
Motivation: I've come across a short blog text, where the ...
- 152
0
votes
0
answers
13
views
How to calculate the resolution of spectrometer at the emission edge of a metal in x-ray emission?
I wonder how I can calculate the resolution of the spectrometer from the Al L2,3 X-ray emission edge, and why this method is used to determine the resolution.
2
votes
1
answer
133
views
Density of final states in photon absorption/emission by a hydrogen atom
Consider a hydrogen atom in an electromagnetic field. The Hamiltonian is of the form
$$\hat{H}=\underbrace{\frac{\hat{p}^2}{2m}+V(r)}_{\text{atom}}+\underbrace{\sum_{\vec{k},\sigma}\hbar cka^{\dagger}...
- 1,515
1
vote
3
answers
67
views
Electron absorption of photons at varying energies
I am trying to understand the absorption of different energies/frequencies of light by electrons, and I have a few questions (I am relatively new to quantum mechanics, and may have some fundamental ...
- 13
1
vote
0
answers
25
views
Material that is one-sided translucent [closed]
Is there a polymer material that is translucent from one side but not from the other side?
I want to build some custom push buttons that should appear completely black. Only when they are led by an ...
- 111
3
votes
1
answer
66
views
Can we think of spontaneous emission of a photon from an excited atom as a driven harmonic oscillator problem?
This is a kind of strange question, but I'm wondering, in the context of a fully quantum field theoretic treatment of spontaneous emission, if there is any model or way of calculating the process that ...
- 145
2
votes
1
answer
41
views
How is the stimulated emission in lasers initiated?
I know in a 3-level laser system for example, electrons get excited from the ground level to the pump level from which they spontaneously decay quickly to the upper laser level. The upper laser level ...
- 35
2
votes
2
answers
68
views
Why do different metals glow with different colours if all solids have the same emission spectrum?
Why do different metals glow with different colors if all solids have the same emission spectrum? According to my teacher, all solids have the same emission spectrum at the same temperature due to ...
- 411
0
votes
0
answers
23
views
How can there be absorption and reemission of photons when there is a coherent part of the resonance fluorescence radiation?
When we expose a 2-level system to monochromatic light and we are in the stationary state of resonance-fluorescence, the atom radiates into all space.
A part of the light that is emitted from the 2-...
- 6,447
2
votes
2
answers
133
views
If all matter can emit at all wavelengths, can all matter absorb at all wavelengths too?
Based on Planck’s law all matter can emit at all wavelengths at different intensities dependent of temperature. I was wondering if this holds true, does all matter absorb all wavelengths too, at ...
- 411
0
votes
1
answer
33
views
Do gases emit radiation at all wavelength? [duplicate]
According to Planck's law, all matter emits radiation at all wavelengths but is this statement true for gases and pure elements? Gases like hydrogen and helium have specific emission spectrums and I ...
- 411
2
votes
1
answer
48
views
Do all matter emits radiation at all wavelengths? [duplicate]
Does all matter emit radiation at all wavelengths? Do gasses also emit radiation at all wavelengths since they have a specific emission spectrum? Shouldn't they only emit radiation according to their ...
- 411
6
votes
1
answer
446
views
Is the Sun considered to be a black body as a whole or it is only the photosphere which is a black body?
I am having some difficulties understating how fusion inside the Sun is connected to the Sun being a blackbody. How do the photons transfer to the photosphere? Is the amount of transferred energy less ...
- 411
4
votes
1
answer
82
views
What are the absorption and emission spectra of $\rm H^+$ ion (a proton)?
Does $\rm H^+$ even produce emission spectrum without an electron?
- 111
0
votes
1
answer
22
views
What accounts for a Lyman-break for all wavelengths shorter than 91.2nm if the Lyman limit is the highest energy photon that Neutral hydrogen absorbs?
From this description of Lyman-break galaxies, I don't understand how:
...radiation at higher energies than the Lyman limit at 912 Å is almost completely absorbed by neutral gas around star-forming ...
5
votes
0
answers
67
views
Can an LED emit photons with energy (in $\rm eV$) larger than the voltage drop across it (in $\rm V$)?
I recently had a discussion with someone who told me that they have a UVC (260 nm - 270 nm) LED with a forward voltage of 3.3 V. I told them that this must be impossible, because an electron dropping ...
- 51
0
votes
0
answers
27
views
Derivation of Moseley's Law
I've been going around Moseley's law for characteristic emission of X-rays. Everything up to the derivation seems straight-forward, but I cannot see the sense in the explanation for the $(Z-1)$, that ...
- 399
1
vote
2
answers
79
views
Spin of electron and photon emitted
How does the spin state of the electron affect the polarisation of the light emitted?
I am looking for a description in a detailed mathematical aspect, any suggestions on books ?
- 106
0
votes
0
answers
15
views
Why is saturation current a function of intensity?
I know from this question that a saturation point exists because beyond a certain point no more electrons can be emitted beyond a point due to the accumulation of charges, if this is the case, why ...
9
votes
4
answers
1k
views
Why can Einstein coefficients be derived based on thermodynamically equilibrium relations when they are basically intrinsic?
Einstein coefficients for emission and absorption ($A_{21}$, $B_{12}$, $B_{21}$) are often derived from a consideration of thermodynamic equilibrium using Boltzmann statistics and comparison with ...
- 961
0
votes
0
answers
20
views
Spontaneous emission between two parallel plates
I try to find analytical derivation for the expression of the Green function describing the EM coupling between two plates of metal. From what I've found in [this paper][1],the decay rate when the ...
- 21
1
vote
1
answer
32
views
Trouble with Einstein coefficients - what is the meaning of the transition probability?
Perhaps it seems to be a not very intelligent question, but I am unfortunately not able to understand what the probability per second that a molecule will absorb a photon is, as part of the theory of ...
- 63
3
votes
2
answers
105
views
Can there be some kind of photon emission caused by cosmological expansion?
Are there any kind of observed and experimentally verified processes or mechanisms where photon emission occurs and which are directly cause by spacetime expansion in some way?
- 1,316
0
votes
0
answers
32
views
Quantum model for excitation of electronic states by application of electric current/power
What is the quantum mechanical model/description for excitation of systems via application of electric power/current? Consider for example your display that you look at while you read this. The system ...
- 2,142
0
votes
0
answers
13
views
Is it possible to calculate ion species fractions from relative intensity optical spectra?
I'm trying to find references or instruction on how to calculate or at least estimate the ion population or population fraction from the optical spectra of a plasma.
I have found tables that provide ...
- 33
2
votes
2
answers
56
views
Why do electrons come to ground state even after giving absorbing energy?
Imagine you have a hydrogen placed under sunlight, now if we look at 1st shell of hydrogen, it has energy of $-13.6$ev now for 2nd shell we have energy of $-3.4$ev.
1st shell -> $-13.6$ev
2st ...
0
votes
0
answers
72
views
Can Two Electromagnetic waves cancel each other if it 180 degree phase moving in same direction?
If we can send two electromagnetic waves -180 degree out of phase- in same direction, then the interaction of this wave with air molecules will be less due to the low intensity of the combination. So,...
- 33
0
votes
1
answer
54
views
How exactly does one reaction of nuclear fussion exactly produce EMR of different types? [closed]
Electromagnetic radiation from sun is more likely produced by the nuclear fusion, and at a go radiation is released but how is it possible for different types of radiation to be produced such as, ...
- 113
1
vote
0
answers
18
views
Helicity conservation during nuclear resonance in Goldhaber Experiment
Within the context of the Goldhaber Experiment. If a polarised photon of helicity $\pm 1$, is used to excite a $^{152}Sm$ Samarium nucleus to an excited state $^{152}Sm^*$, that then, by spontaneous ...
- 472
7
votes
1
answer
488
views
Does each spectral line of an atom/molecule have a unique lineshape?
A spectral line is determined by a particular transition in an atom or molecule. In reality, this line isn't infinitely sharp, but has a small distribution about the resonance frequency as a result of ...
- 139
0
votes
1
answer
66
views
Is refraction unpredictable?
Let us take a simplified version of refraction, where light slows down because of atom absorption and re-emission. Let us denote this time as $\tau_{emission}$, do we have a function $\tau_{emission}(\...
0
votes
0
answers
20
views
Responsivity of a photo detector
I have a pn junction diode of which responsivity (R = Photocurrent / optical power) is to be calculated. For this purpose i have 5 LEDs of various wavelengths (UV, RED, BLUE etc).
In this case, i ...
1
vote
3
answers
78
views
Electrons in Atom in different energy states
I have a very basic doubt in Bohr's Atomic Model.
I just studied that an electron can go to any Energy State with in the atom, by getting relevant energy from photons.
If an electron goes to 2nd ...
0
votes
1
answer
26
views
Will annihilation occur when two electrons and a positron are released at once to collide against each other?
suppose free Two electrons and a positron are released at once in space to collide against each other,will there be annihilation ?or there will be no annihilation due to imbalance of matter and ...
- 23
1
vote
2
answers
51
views
Photoelectric emission at frequency less then threshold frequency
If I shine an EM radiation of frequency $\nu$ on a metal surface which has threshold frequency of $\nu_o$, where $\nu < \nu_o$ then, will the emission occur by multi photon absorption?
My reasoning ...
0
votes
1
answer
22
views
Thermally activated delayed fluorescence
In thermally activated delayed fluorescent (TADF) molecules, we consider 25% molecules in singlet first excited state and 75% in triplet, statistically, on electrical excitation after carrier ...
2
votes
1
answer
355
views
Purcell effect for large cavities
The model of interest is a 2-level system (e.g. an atomic transition) inside a damped single-mode cavity.
The purcell effect states that the atomic decay rate inside the cavity $\Gamma_{cav}$, on ...
- 33
0
votes
0
answers
19
views
Terahertz generation in semiconductors after ultrafast laser excitation
Terahertz can be generated by means of the photo-Dember effect, where a short laser pulse generates electrons and holes. These charge carriers have a different mobility which gives rise to a dipole ...
- 205
0
votes
0
answers
33
views
Selection rules for electronic transitions when noble gas atoms collide
The selection rules of atoms that are alone are useful for determining whether there can be certain radiative transitions, or which transitions are more likely than others. For example, for small ...
- 1,350
0
votes
0
answers
61
views
Is the $(1s)(2s)$, $S=1$ excited Helium state metastable?
I am reviewing properties of atoms, and I am trying to understand the concept of forbidden transitions better. My understanding is mostly at the level of Griffiths quantum mechanics.
My motivation is ...
- 1,350
0
votes
0
answers
22
views
Where can I find data of a UV blocking glass absorption filter absorbing the visible light and re-emitting the energy as a photon of NIR?
If I understand correctly, a UV Transmitting, visible light absorbing colored glass absorption filter absorbs the visible light energy and re-emits it as near IR. On Oct 16, 2013 in How does Infrared ...
0
votes
1
answer
58
views
Why does light behave differently when interacting with multiple particles?
When light hits an atom (I will use a carbon atom for simplicity), if it is not in the absorption and/or emission spectrum of carbon, it will simply pass through without interacting with the atom. ...
- 115
0
votes
0
answers
38
views
Why does light not pass through opaque objects? [duplicate]
Since light is massless it does not interact with particles unless that specific wavelength is on the emission and absorption spectrum.
The emission and absorption spectrum of an atom indicates the ...
- 115
-3
votes
2
answers
134
views
At what point of approach in annihilation process the charges of antiparticles disappear? How is relevant to the electron-proton interaction? [closed]
For me it is incomprehensible that from the indisputable fact that a free electron - like a proton - carries a constant charge with it, one transfers this empirical finding to bound electrons (protons)...
- 9,283
1
vote
1
answer
143
views
What are the differences between electron-positron annihilation and proton-electron scattering?
To me, the beginning of the approaching of an electron-positron pair and an electron-proton pair look somehow the same. There is a spatial attraction and in the process there is an energy emission in ...
- 9,283
1
vote
0
answers
47
views
How photon beam can be attained through Proton Accelerator?
I'm recently had been reading quite a lot about ADS and transmutation possiblity of Proton beam to neutralize nuclear waste. I came across with an Article from Big THINK https://bigthink.com/the-...
- 21
0
votes
0
answers
40
views
Calculation of the rate of transition of the Hydrogen electron from $|2lm\rangle$ to ground state
This is how it was calculated in my book:
We take the electromagnetic field to be part of the system. The initial state of the system is the direct product $|2,l,m\rangle \times |0\rangle$. $|0 \...
- 5,782
0
votes
3
answers
305
views
How do objects emit light?
I recently bumped into a question of how things emit its color. And I've gone through some articles on the internet to be now stuck between two phenomenon: reflection (I'm not sure if its called this ...
- 49
1
vote
0
answers
22
views
Spectral Line Intensities of a sample
I am doing some research on the flame test and I get the main point. I was wondering, how do you calculate the rate of photons emitted vs frequency. When I look at the Sodium emission spectrum, There ...
- 11