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. Erik Ayer

    I Mach-Zehnder with Stimulated Emission

    Imagine a Mach-Zehnder interferometer adjusted so that light comes out one face of the final beam splitter, as per normal use. In the arms, lasing material is added so that photons can cause stimulated emission of more photons that should be the same wavelength and in phase - they should be...
  2. Haynes Kwon

    I Absorption lines and emission lines in stellar spectra

    Why do we see more absorption lines in stellar spectra than emission lines?
  3. J

    I Thermal photons emission inside a material

    in the inside of the material is heat also can transferred by radiation?
  4. O

    B Question about EMF and EEG emission

    1. how do you block or interfere with the emf(electromagnetic field) emission generated by your brain? 2. how do you block or interfere with an EEG taken from the mind(what factor influence EEG taken from the mind and can add noise to the signal?). 3. Regarding US Patent 3,951,134 "Apparatus...
  5. B

    Hydrogen emission spectrum calculation

    I've first method I tried was using f = v/λ to find the frequency, then E = hf to find the energy and then using E = (-13.6eV/n^2) - (-13.6eV/n^2) to rearrange and solve for the unknown n. However I got 5, the same as the original entry level. I also tried using 1/λ = R(1/4 - 1/n^2) to solve...
  6. HibyPrime

    B Gravitational wave emission from electrons

    Ok, so I've been on a kick trying to really understand why QM and GR are incompatible. I think I get that GR can't be realistically converted into a quantum field because it creates some infinite series that you can't use the normal tricks you would for other QM fields. Hard block, ok got it...
  7. bhobba

    I Why Do We Have The Effect Of Spontaneous Emission And Absorption

    Hi All In another thread I answered was a question related to this and noticed another as well, so I thought I would give the full answer in its own thread rather than write it out twice. The other question has been deleted but here is the full detail anyway. First see...
  8. F

    I QED & In-Ground Electrons: Why No Photon Emission?

    In ground state electron does not emit photon.Can we use QED to explain why in ground state electron does not emit any photons?
  9. N

    Does radioactive decay exhibit stimulated emission?

    If you have a lump of the same species of radioactive isotopes, why can't the photons emitted from the radioactive decay of one nucleus cause spontaneous emission from other atoms? I presume it doesn't, because if it did, there would be a geometric effect of radioactive decay, which is not...
  10. Adrian Tudini

    Infrared emission of Lithium Nitrite (LiNO2)

    Hi i am trying to find the infrared emission spectrum of Lithium Nitrite on the web but having no luck. Has the spectrum been measured? If so, can I be redirected to the resource? This for general interest and a personal project. Thanks.
  11. B

    Electric field of light emitted by atom, given the intensity

    For t < 0 , all I can think of is a qualatative " the field is zero because the intensitity is 0 when the burst of light hasn't been emitted yet " For t >= 0 , I've tried squaring the given E and that let's me say the amplitudes are proportional (with a cos^2 term in the mix) But I feel like...
  12. DaTario

    A Increase of coherent length in stimulated emission

    Hi All, When I teach the basic structure of a laser setup, stimulated emission appears as a fundamental phenomenon. But in no reference I found a description that could account for the increase of coherent length of the EM laser field. According to my knowledge, one photon typically doesn't...
  13. P

    Calculating Emission Wavelength for Excited Atoms at 3.031x10^-19 J Energy Level

    Problem Statement: A sample of excited atoms lies 3.031×10^−19 J above the ground state. What is the emission wavelength of these atoms? Relevant Equations: E=hc/λ λ=hc/E I'm stuck on the first part. i.e; something / 3.031x10^-19J
  14. riodice

    Question about PET scans (Positron emission tomography)

    I understand that a PET scan will produce Positrons which will come into contact with an electron and produce Gamma rays in the area where there is a high uptake of sugar (assume glucose). In this process of annihilating an electron, some poor atom will lose an electron which I assume would...
  15. B

    Photoelectric Effect versus Laser Stimulated Emission [Confused]

    Our teacher taught us "Laser" today and it made me confused. So Electron s energy in n=1 is around 13 eV (-13eV) and in n=2 is around -3.4 eV. Our teacher told us if we radiate a photon which has 9.6 eV energy (the difference energy of the first and second layer, n1 and n2, which is 13-3.4=9.6...
  16. Abimbola1987

    Thermionic emission and current density

    Dear Sirs, Maybe this is general knowledge, but I couldn't find the answer where I looked, so please bear with me. Consider a circuit consisting of a mechanical generator (some spinning magnets and coils) and a wire across the generators output. At some point the wire gets hot and starts a...
  17. S

    Rate of emission of alpha particle in uranium decay

    Homework Statement U - 238 is undergoing alpha emission into Th - 234. U - 238 has half – life of 109 years. Calculate the emission rate of alpha when uranium has mass of 10 grams Homework Equations A = λN A = A0 (1/2)n , n = t / half - life The Attempt at a Solution Not sure how to do it but...
  18. A

    I How does stimulated emission work in the process of light amplification?

    I understand the concept of stimulated emission and how it works as light amplification, but a certain technicality in its process eludes me. How is the inciting photon actually interacting with the electron that falls to a lower energy level? In every physical interaction that I know of there...
  19. S

    Correct graph of current vs voltage (photoelectric emission)

    Homework Statement The diagram shows a circuit used for the investigation of photoelectric emission. The two electrodes E and F are made of different metals. The work function of electrode E is higher than that of electrode F. Which of the following graphs show the variation the current...
  20. P

    B Speed of Light -- Why doesn't it add to the speed of the emission source?

    My question is about the speed of light. Our current understanding of light says that light is constant for all observers, and uses time dilation to explain this. Have we proven this? The speed of light emitted from a stationary object is equal to C. The speed of light emitted from a moving...
  21. A

    MHB Calculating New Emission Rate of Radioactive Source

    A radioactive source emits particles at an average rate of 1 pe second. Assume that the number of emissions follows a Poisson distribution. The emission rate changes such that the probability of 0 or 1 emission in 4 seconds becomes 0.8. What is the new rate? Thanks.
  22. Imager

    B No low-frequency emission from Fast Radio Bursts

    I didn't see where anyone else had brought this up. From the article: The telescopes are the Murchison Widefield Array (MWA) and the Australian Square Kilometre Array Pathfinder (ASKAP), and they were synchronized to observe the same patch of sky, searching that area for fast radio bursts...
  23. S

    I How Would Electron Entanglement Affect Photon Emission

    Suppose you have a pair of electrons in the same quantum state, and are thus spin entangled, and they absorb a pair of photons and release them at the same time. How would this affect the photons? Would the photons be entangled? Would it affect the photon spin, and if so, how would it affect the...
  24. Eric Bretschneider

    Emission of light from a surface

    I came across someone in the lighting industry who insists that because of Gauss's divergence theorem and Maxwell's Laws that when light is emitted from a surface that it is only emitted orthogonal to the surface. I have tried to point out numerous real world examples that contradict the...
  25. Jim Fern

    Energy lost through photon emission

    Hey guys, new here. Here is my first question for the forums: Let's say that I have a controlled environment for an experiment whereby I want to heat, say, one cubic centimeter of steel until it is white hot. Assuming that I have perfect containment set up for it such that no energy can be...
  26. mesa

    Looking for excited state gamma emission data on everything?

    Hey guys, I am looking for a database on gamma emission from the first few excited states of known isotopes for a piece of software we are putting together. Any format is fine. Thanks!
  27. A

    Why is solar radiation equal to long wavelength emission?

    In my heat transfer course, I always had to do analysis of long-wavelength radiation between surfaces first, and find the heat radiated from one of the surface. Then, solar radiation is added to the problem, and suddenly it was said that solar radiation=heat radiated from this surface! Does...
  28. S

    I How to differentiate Doppler shift from star emission

    I have seen people talking about measuring Doppler shift of stars to know how fast they are receding from us. But if I measured say a particular frequency f, how do I know whether this is shifted frequency or just the emission?
  29. F

    I What Happens When Photon Energy Differs in Stimulated Emission?

    Please teach me: if stimulate photons have energy different from the difference of two energy levels of atom then what is happened?What is coefficent of the stimulate emission in this case?
  30. O

    Light Emission from Materials in MCNP Simulations

    Hi, I am trying to model the distribution of the light emission from a material when excited with neutrons in MCNP. I have been searching literature and found not many things. Could anyone provide me with sources from which I can get info? Thank you in advance.
  31. P

    THz Radiation, Antennas: Need background knowledge

    I want to use small molecular - preferably CNT - "antennas" to produce THz signals to monitor activity in biological systems. After some googling, I've been reading things like "absorption spectra", "energy bands", "spectroscopy", as well as a bunch of antenna-science related jargon... I need...
  32. P

    Stimulated emission per second per atom?

    Homework Statement We are investigating hydrogen in a plasma with the temperature 4500 ºC. Calculate the probability per atom and second for stimulated emission from 2p to 1s if the lifetime of 2p is 1.6 ns Homework Equations Planks radiation law: ##\rho (f) = \frac{8* \pi...
  33. Alianos

    Emission cross section and laser performance

    How does the emission cross section of an emitting atom (such as Yb atoms in glass) affect the laser performance, namely the slope efficiency (signal power vs absorbed pump power) and laser threshold? Thanks a lot
  34. B

    I What is the Average Angle of Infrared Emission from a Flat Diamond Surface?

    does anyone know what is the average angle of infrared emission is by a flat diamond surface or tha directional distrabution
  35. P

    Probability per atom and per second for stimulated emission to occur

    Homework Statement We are investigating hydrogen in a plasma with the temperature 4500 ºC. Calculate the probability per atom and second for stimulated emission from 2p to 1s if the lifetime of 2p is 1.6 ns Homework Equations ##A=\frac{1}{\Sigma \tau}## $$A_{2,1} = \frac{8*\pi *h *...
  36. S

    A Emission line core in sunspots

    What makes the core of some chromospheric lines such as the transition at 8542 A of the infrared Ca II triplet appear in emission in the dark umbra of sunspots?
  37. M

    Understanding an electron's emission of electromagnetic waves

    Hi to everybody ! I was thinking about something which confuses me about wave emission. The question is simply the following: Does an electron emit light when it accelerate? or just during its deceleration? or maybe when acceleration and deceleration alternates in some order? I'm not really...
  38. H

    How does thermionic emission work?

    I’ve been curious about understanding the mechanism behind themionic emission from what I have read I found that themionic emission happen when the energy from added temperature excess the work function of the material. I also readed when temperature excesses 1000k themionic emission happens but...
  39. L

    A Calculating the spontaneous emission rate for a material

    Hi, Suppose I have a 1D material of length L, and I want to calculate the spontanious emission rate Γ at ressonance frequeny. From my understanding, when light passes in a material at ressonance frequency it gets absorved by an electron in the atom, and after a spontaneous emission time tspont...
  40. K

    Black Body vs Non-Black Body: What Sets Them Apart in Kirchoff's Law?

    Homework Statement For a black body all absorbed radiation is emitted. Kirchoff´s law states that at the same temperature T1 the emissivity and absorptivity of a surface are equal, which holds for nonblack bodies as well. So, what really differs a black body and a non-black body in this case?
  41. F

    I Planck Emission Spectrum

    Hello Everyone, I have some thoughts about Planck's law. The graph describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. I think the absorption (or absorbance?) spectrum of an ideal blackbody should be a horizontal...
  42. S

    I Emission lines and absorption lines

    Why more emission lines than absorption lines are usually observed in the atomic spectra of most elements hence explain why this occures?
  43. G

    What does a body "emits" when falling down?

    I explain it better. If we bring an electron from higher to lower energy level, the energy gap will be emitted as electromagnetic wave, because of the conservation of energy. When the same situation applies for a physical body, for example letting if falling down from some height, what does it...
  44. S

    Difference between emission due to absorption and reflection

    What is the difference between the photon interaction mechanisms in emission due to absorption and reflection?
  45. S

    A Semi Classical Explanation of Stimulated Emission

    Can Stimulated Emission in lasers be explained semi classically? If so, how?
  46. jishnu

    I Emission of neutrinos and antineutrinos

    My question is what is the actual purpose for the emission of neutrinos and antineutrinos during the beta + and beta - decay of an atom respectively?
  47. A

    I Photon emission, power output (and black holes)

    I recently re-read an article by Muller (https://arxiv.org/pdf/1606.07975.pdf) about the flow of time, and the possibility of time reversal given sufficient energy dissipation (basically during black hole evaporation, he concludes). Although the paper is on arXiv and not peer reviewed, Muller...
  48. physics loverq

    B What is the underlying reason for stimulated emission?

    I learned that stimulated absorption, spontaneous emission and stimulated emission are three fundamental concepts in the process of radiation. Among these three concepts, I found stimulated emission really hard to comprehend, it says when atom in its excited state is stimulated by external...
  49. M

    I Why don't absorption and emission spectra "cancel out"?

    My question is regarding absorption and emission lines. As far as I understand, when a photon of the "right" wavelength passes through an atom, an electron is excited and takes on a higher energy state, in proportion to the energy imparted by the photon. This is the "absorption" part. However...
  50. S

    Beta emission momentum problem

    Homework Statement C14 disintegrates by b-emission with a reaction energy (q value) of 0.155 MeV. A b-particles with an energy of 0.025MeV is emitted in a direction at 135° to the direction of motion of the recoil nucleus. Then the momenta of the three particles (b = V, 14N) involved in this...
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