What is Emission: Definition and 566 Discussions

The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an atom or molecule making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum. Each element's emission spectrum is unique. Therefore, spectroscopy can be used to identify elements in matter of unknown composition. Similarly, the emission spectra of molecules can be used in chemical analysis of substances.

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  1. dumpling

    I Exploring the Relationship Between Light Emission and Wavefunction: An Analysis

    Hi! I would like to wrap my head around a relatively simple issue. Lets say that you have an excited atom, which rests in your refernce frame. When it emits light, the atom will have a backreaction, and it will "gain momentum" with the opposite direction as the photon. Of course, without...
  2. E

    I Only certain emission lines show up in absorption spectrum

    I'm reading Eisberg's Modern Physics and in it, in the atomic spectra chapter, he says: "We have been discussing the emission spectrum of an atom. A closely related property is the absorption spectrum. This may be measured with apparatus similar to that shown in figure (5-1) except that a...
  3. P

    A Reflection or emission of a photon

    Hi, if I read the article (see link) I get confused: Is it emission or reflection? If it is emission, how is it possible that the photons are emitted to one side? (Unfortenately I do not have access to the original article.)...
  4. S

    B Why do photons stimulate emission in atoms?

    I can't get my head around stimulated emission.Why does a photon traveling towards an atom stimulate emission? The best way I could answer is that a photon has an electro magnetic field and this causes an excited atom to oscillate.This induces an excited electrons to fall down an orbital. But...
  5. Spinnor

    B (N+1) enhancement of spontaneous emission, why not (N+1/2)

    Feynman tells us, "The probability that an atom will emit a photon into a particular final state is increased by the factor (n+1) if there are already n photons in that state." 4–4 Emission and absorption of photons, http://www.feynmanlectures.caltech.edu/III_04.html The 1 in (N+1) comes from...
  6. A

    B What is the equation for proton emission after muon capture in heavy nuclei?

    Can anyone tell me what is proton emission equation after muon capture for heavy nuclei?is it same with neutron emission equation??
  7. J

    I I use an Olll filter to view emission nebula -- how do they work?

    I use an Olll filter to view emission nebula such as the Great Nebula in Orion. What is the mechanism by which Olll in such nebula emit photons of the wavelength that passes through my filter?
  8. J

    Which Letter Represents a Star Similar to the Sun Based on Emission Spectra?

    Homework Statement [/B] The top spectrum shows part of the Sun's spectrum. State and explain which letter best represents the light from a star that is similar to the Sun. Homework Equations None. The Attempt at a Solution I originally was thinking A but my book says B but only gives...
  9. E

    I What's the interval between photons in stimulated emission?

    What's the interval between photons in stimulated emission? In stimulated emission one photon induces the emission of a second photon whose coherence length, energy, polarisation and direction of travel are all identical to its own. There must be a delay between the two photons, see below, so...
  10. yeshuamo

    What is the Physical Situation Described by this Unidentified Transition Rate?

    Homework Statement I am identifying equations on the final exam equation sheet for my quantum II class. I've identified them all except this one, what I am guessing is a transition rate for some kind of emission or absorption of radiation case. Please help me identify the physical situation...
  11. G

    B Why is a black surface a better emitter of IR than a silvered surface?

    I can just get the idea of a silvered surface reflecting IR and a black surface absorbing IR (analogous to how light behaves) but I can't see how a silvered surface, if warm is a poorer emitter than a Matt black surface, if warm? Would appreciate any help without going too in depth. Regards, G.
  12. K

    B What happens to absorbed colors in colored substances?

    They say that substances have color because when light waves of all colors hit the substance, the atoms do absorb all the colors, except those that is its color. Red substance is red because it absorbs all the color waves, but reflects the red waves. But all the color waves the red substance...
  13. S

    The emission spectrum of an unknown element

    Homework Statement The emission spectrum of an unknown element contains two lines - one in the visible portion of the spectrum, and the other, ultraviolet. Based on the following figure and what you have learned about Niels Bohr's model of the atom, account for the difference in energy between...
  14. SchroedingersLion

    A Enhancing Spontaneous emission in a vacuum standing wave

    Hi, it is well known that spontaneous emission of an atom can be enhanced, if the atom sits at a node of the vacuum standing wave field in a cavity. My question is, why is it the node? At a node of a standing wave, there is zero intensity, so there should be no interaction between the atom and...
  15. EspressoDan

    Light - Black-bodies & Spontaneous / Stimulated Emission.

    Hello, I have a short question: In relation to the Sun - is Black-body radiation ultimately the result of a combination of spontaneous (majority) and stimulated (minority) emission of photons? In relation to the IR emissions from everyday objects due to their temperature - is Black-body...
  16. C

    Interference of light, emission spectroscopy prac. report

    Ok, so I've got a practical report due tomorrow and I just wanted to clarify a few things. A bit of background knowledge first. The practical involved taking angular measurements for the emission lines of the Mercury spectrum using the apparatus, a spectrometer and a Mercury spectral tube...
  17. H

    I Can Emission Theory Produce Doppler-Shift Formula?

    Emission theories propose that the velocity of light depends on the velocity of the light source. But the ordinary Doppler effect assumes the velocity of light remains as ##c## with respect to the ether medium, even when the light source is moving at speed ##v## with respect to the ether. They...
  18. ISamson

    I Emission Spectra: Gas Temperature & Glass Prism

    How hot does a gas have to be to achieve its emission spectrum with a glass prism?
  19. Z

    Investigation about the emission spectrum of Mercury

    Homework Statement For our investigation, we used a diffraction grating spectrometer to observe the emission spectrum of mercury. We conducted the experiment in a pitch black room to avoid any unwanted light pollution, etc. Whilst conducting the experiment we observed a number of 'faint' lines...
  20. T

    I Frustrated spontaneous emission

    I have heard of frustrated spontaneous emission that somehow says that an atom that normally emit light will cease to do so when its surroundings is incapable of absorbing light. How is this possible, and is this experimentally proven?
  21. Alfredo Tifi

    I Einstein clock syncing with one way light emission absorber

    Two spaceships with their engines shut off and identical radio receiver-amplifier-reemitting devices are in the empty space, very far from each other and from any celestial body. The lag time from absorbing to reemitting in the device is vary small compared to the return time of the signal (2t)...
  22. A

    B Fusion and Alpha Particle Emission: Neutron vs Proton

    When two deuterons fuse, I understand they form an alpha particle in an excited state. Based on mass differences the fusion releases 23.85MeV, which is enough to eject a proton (19.81MeV) or a neutron (20.58MeV) from the alpha particle. It seems to prefer neutron emission, as this fusion is used...
  23. T

    B Why only certain colors in emission spectrum are visible?

    Why are only certain colors of the emission spectrum in Hydrogen visible?
  24. BillTre

    New Concept for Zero Emission Natural Gas Power Generation

    Science mag news article on a new electrical power plant being set-up by a start-up. It burns natural gas with pure oxygen and runs turbines with CO2. It makes water rather than using it and is in theory close to competitive economically. . Sounds good to me, but I'm no engineer.
  25. A

    I Change in electron energy level and photon emission....

    Hi all, This is likely a naive question, following up on something @vanhees71 posted some time ago in another thread: My question is the following - if we take an electron that has, for example, absorbed a photon, is the portion of the wavefunction representing the electron in a lower energy...
  26. J

    I Emission spectra of different materials

    I have some more detailed questions on this further on but I found it better to start with a very basic question first: If higher temperature is correlated with shorter emitting wavelengths, how come there are incandescent light bulbs that emit yellowish light but are hotter than incandescent...
  27. M

    B Thermal and Non thermal light emission

    I am now working on Thermal and Non-thermal light emission of materials, particular concerning the Planck law and Generalize Planck Law. I really want to understand the fundamental concept of this. So could you please suggest me some material, book on this subject? Thank you so much in advance,
  28. Klupa

    B Light determination for emission spectrum

    Hi all, the title is probably a bit confusing but I was wondering. What determines the type of light emitted when electrons move down electron shells and emit energy? Why isn't all the light emitted the same colour?
  29. W

    B Related to - Thermionic emission

    Hey currently I am doing O levels and in my textbook I read that when a metallic wire (in CRO - the cathode) is heated up, it starts emitting its free electrons (thermionic emission). And also its a fact that electrons are responsible for electrical conductivity. A question just popped up in my...
  30. Docdan6

    Why an electron at rest cannot emit a photon?

    Hi! Could someone explain to me why an electron at rest without any influence from a magnetic or electric field cannot emit a photon ? Could you explain it mathematically too ? Thanks in advance...
  31. bluejay27

    B Quantum Dot Emission: Band Gap & Heisenberg's Uncertainty

    Why does the quantum dot's band gap increase as in shrinks in size? What is the principle behind this? Is the Heisenberg's uncertainty principle?
  32. G

    I Filament for thermionic emission in open air

    I’m looking for material capable to act as filament of thermionic emitter in open air. Classical tungsten filament is not capable, because it readily oxidizes. We experimented with filaments made from SiC and ZrO2 (Yttria stabilized). At 1900K SiC provides certain degree of emission, but it is...
  33. Karolus

    B What is the fundamental principle behind the operation of a laser?

    The principle of operation of the laser is based on stimulated emission concept. In short, if a suitable energy photon hits the electron of an atom, in which the electron is in the excited state, there is a probability that the electron returns to the ground state. The photon emitted has the...
  34. Q

    I Temperature impact on laser emission

    Hi everyone, I'm trying to understand why laser diodes need a stronger input current to start lasing when their temperature increases. If I tried to add thermal transitions to the rate equations governing the evolutions of an atom quantum level populations (let's say ##n_{up}## and...
  35. R

    I Energy Emission from Black Holes: Exploring the Mystery

    My understanding is that once light or anything else crosses the event horizon, it will not re-emerge. However, we detect high energy beams of radiation coming from opposite sides of some of the celestial bodies that I have been told are types of black holes. Obviously I'm missing something here.
  36. T

    Nonreflective Coating and Emission Relation?

    Hi all, I've been able to find the answers to most of my questions in these forums, but this time I was not able to. So here goes my first post: I've been learning about thin film interference, and it all makes sense to me except for the correlation between destructive interference caused by...
  37. ORF

    A How the emission spectra can be affected by E/M field?

    Hello A friend of mine asked me if he could improve the (amateur) characterization of minerals by studying the absorption spectra during the application of a magnetic field. I thought that maybe the electron cyclotron resonance could work, but then I noticed that very low temperatures are...
  38. J

    I Difference between Scattering and Emission of Photons

    Hello, Ok, so I’ve been searching about this for a while and there seems to be a difference in explanations that confuses me. What concerns me is the exact detailed physical mechanism that makes particles cause a scatter of a photon and an emission of a photon. The Wiki page about scattering...
  39. amarante

    I 21 cm emission in a laboratory

    Hey, I kind of understand the process of the 21 cm emission of the atomic Hydrogen, I know how rare it should be but still it is detectable in our Galaxy due to the huge amount of atomic hydrogen it has. However, I was wondering if it is possible to detect the 21 cm emission line in a...
  40. G

    I Trying to understand how spontaneous emission works

    I'm reading Gerald Folland's "Quantum Field Theory: A Tourist Guide for Mathematicians" and I'm up to Section 6.2 which is called "A toy model for electrons in an atom". He has a nonrelativistic particle of mass M and a scalar field with quanta of mass m and the state space for the particle is...
  41. G

    I Ratio between spontaneous/stimulated emission

    Hi. In thermodynamic equilibrium, the ratio between spontaneous and stimulated emission is $$\frac{A_{21}\cdot N_2}{B_{21}\cdot N_2\cdot u(f)}=e^{\frac{hf}{k_B T}}-1$$ where ##A_{21}## and ##B_{21}## are Einstein coefficients. This means, that there's always much more spontaneous than...
  42. P

    EM Field Angular Momentum Emission Without Emitting Energy?

    To radiate energy, the Poynting vector must not drop faster than with the inverse square of the distance. Under what circumstances can EM angular momentum be emitted to the vacuum of space (i.e. without being recovered via inductive coupling) and yet not lead to energy losses through radiation...
  43. J

    A Accelerating particle photon emission mechanics?

    It's been a while. But I have always received the help I needed on this forum. I had this question in my head, When a particle accelerates, it creates an oscillating electric field, and a photon. How much does this effect, affect the energy of the particle itself? Say I had a particle...
  44. T

    A Do we need Lindblad operators to describe spontaneous emission

    In Griffith and Sakurai QM book, spontaneous emission is treated as a closed system subject to time-dependent perturbation. Yet in quantum optics sponantanoues emission is treated as in the form master equation of density matrix. Even in two levels system where there is only one spontaneous...
  45. T

    A Difference between ASE and stimulated emission

    Is there any inherent difference between amplified spontaneous emission and stimulated emission? Is not stimulated emission simply the mechanism by which ASE occurs? Is stimulated emission just a broader term? I've read the two terms in literature and just wanted to ensure I understood the...
  46. bluejay27

    I How Do Quantum Dots Emit UV Light?

    If quantum dots are placed within the body, what is the excitation needed for us to observe its emission? X-rays? I have heard that Quantum dots are used in solar cells. How does the process work for the conversion of light to electricity? I also heard that Quantum dots can emit ultra violet...
  47. moenste

    Alpha emission decay: maximum possible delay

    Homework Statement A tube containing a isotope of radon, 22286Rn, is to be implanted in a patient. The radon has an initial activity of 1.6 * 104 Bq, a half-life of 4 days and it decays by alpha emission. To provide the correct dose, the tube, containing a freshly prepared sample of the...
  48. nucleon

    Confused about magnesium's and calcium's emission spectra

    I have read that magnesium’s flame is white, and the light emitted includes all the wavelengths of visible light. Calcium, on the other hand, needs less energy to excite its valence electron, and hence, during emission, the radiation given off has a longer wavelength (red light) and its flame is...
  49. allenlistar

    Calibrate Spectroscope to Find Wavelength

    Homework Statement A student collects diffraction data using a lamp with known emission wavelengths of 425nm, 565nm, 600nm, and 700nm. These lines appeared on her spectroscope at 32mm, 59mm, 63mm, and 69mm(all measured from the same arbitrary 0mm position). With these data she is able to...
  50. S

    A Probability of photon emission from quantum dot

    Hi guys, I am looking for a formula which I am sure exits but I cannot locate it. The problem is that a quantum dot absorbs a photon of wavelength λ0(dot is semiconductor or could be any other material). Assuming that it reemits a photon, what is the probability that this emitted photon will...
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