What is Emission: Definition and 563 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. druscilla

    Rate of EM emission based on surface characteristics

    I would think the black painted surface is
  2. S

    Flicker emission limits

    Do Psti and Plti values decrease when the measured Pst and Plt (@LV) is transposed to HV?
  3. T

    I Fourier Transform of Photon Emission Hamiltonian

    Hey all, I just wanted to double check my logic behind getting the Fourier Transform of the following Hamiltonian: $$H(x) = \frac{ie\hbar}{mc}A(x)\cdot\nabla_{x}$$ where $$A(x) = \sqrt{\frac{2\pi\hbar c^2}{\omega L^3}}\left(a_{p}\epsilon_{p} e^{i(p\cdot x)} + a_{p}^{\dagger}\epsilon_{p}...
  4. Paul Howard A

    I Do Emission and Absorption Spectra Match? A Non-Physics Minded Tourist's Guide

    Basic stuff. Do emission and absorption spectra match? If so, why wouldn't hot stellar atmospheres exhibit both, cancelling? I'm a tourist...not physics minded..
  5. Pushoam

    Spectral lines in the emission spectrum for an electron at n= 3

    Since there is only one excited electron, it could come from n=3 to n =1directly or n=3 to n =2 and then n=2 to =1. Hence, there could be one or two lines depending upon the path taken by electron. Is this right?
  6. Mr Fallspring

    I Double-Slit Experiment: Does rate of photon emission matter?

    Hi there! High school physics teacher hoping to pick the brains of people who know more than I do here. I'm curious whether the rate of photon emission has any noticeable effect on the diffraction pattern generated by the double-slit experiment. To be clear: I understand a diffraction pattern...
  7. B

    I Emission of light from incandescence of metals

    a. We know metals emit EM radiation upon heating or electric current. I'd like to understand more fundamentally how this phenomenon takes place, on the basis of the basis of band structure, and which electrons are involved ? b. Classically, charges emit radiation when accelarating or...
  8. S

    I Can there be some kind of photon emission caused by space 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?
  9. warhammer

    Question on Emission Spectra/Spectral Series | Atomic Physics

    (I need help with the 2nd part as I can answer the theory part properly). For E=4 eV we can find the wavelength of emitted photon. E= 4 eV = 6.4087e-19 J Using E= hc/λ we get λ=310 nm (approx) My doubt is that this should fall in the Balmer Series but we know that the lowest wavelength value...
  10. sol47739

    A Cause of spontaneous emission?

    I am reading this chapter 3 from the book called The Quantum Vacuum by P.Milonni.(Attached in the pdf, look at chapter 3.2 Spontaneous emission) There they say that spontaneous emission is due to both quantum fluctuations and radiation reaction. They say the transitions induced by the quantum...
  11. M

    I Absorption and emission spectroscopy of atoms

    Hello ! As I understand it, the different isotopes of the same atom have a slightly different spectroscopic absorption and emission where, for example, Deuterium absorbs slightly shorter wavelengths than Protium. My question is if two isotopes of different atoms, for example Tritium and Helium...
  12. ure227922

    A Question about stimulated Raman emission

    I have read a paper states that "Stimulated Raman emission relies on damping of the phonon field that is much greater than for that of the optical Stokes field". But I cannot understand this, since all the materials I read do not state this. Can anyone explain it intuitively?
  13. D

    I What determines the time between atomic absorption and emission of photons?

    What determines the time between atomic absorption and emission of photons? Is there a correlation to blackbody radiation?
  14. D

    I Find the interference function for different emission modes

    Homework Statement:: Find the interference function ##I(\delta)## where The emission is analyze by a Michelson interferometer. Relevant Equations:: ##I(\delta) = \frac{1}{2} \int_{-\infty}^{\infty} G(k) r^{ik \delta} dk## ##I(\vec{r}) = I_1 + I_i + 2 \sqrt(I_1 I_i) cos (k\delta)## I have 5...
  15. D

    A Possible Ways to reduce Electron field Emission threshold

    Hello there, i wanted to ask if anyone knows a process or mechanism, that reduces the electric field that is requiered to tunnel an electron. When i use the work function of 4 eV (Aluminum) i get with Schottky-Nordheim approach a field of 870 kV/mm to tunnel an electron. Measurements tho just...
  16. C

    A Absorption and emission spectrum in quantum optics

    The emission spectrum or resonance fluorescence for a quantum dot, atom or defect center are discussed in many quantum optics textbook, for example see "Quantum Optics" by Marlan O. Scully and M. Suhail Zubairy Chapter 10 , "Quantum Optics" by D. F. Walls and Gerard J. Milburn Chapter 10 and...
  17. DennisN

    I Discovery: A radio transient with unusually slow periodic emission

    Paper: N. Hurley-Walker, X. Zhang et.al, A radio transient with unusually slow periodic emission (Nature, 26 January 2022) Abstract: The high-frequency radio sky is bursting with synchrotron transients from massive stellar explosions and accretion events, but the low-frequency radio sky has...
  18. J

    Very High Standard Deviation in Excitation Emission Matrix Measurement

    Hi, I obtain really high standard deviations in Excitation-Emission Spectra mainly for the phenolic compounds in olive oil (Em: 290-350nm). Method: I weigh 0.05g of olive oil and dilute it up to 25ml with cyclohexane to remain in the range of linearity for absorbance measurements to correct...
  19. L

    I Observing Emission Spectra from Computer Screens

    Hi! I am doing some simple observations of different light sources with a simple DIY spectroscope. When I look at a computer screen I see what I believe to be an emission spectrum due to the dark spectrum with emission lines on it. Is this correct? And why does a computer screen emit an...
  20. dbabic

    A Spontaneous and stimulated emission in Planck's radiation law

    Hello, Einstein introduced stimulated emission (along with spontaneous emission and absorption) to derive Planck's radiation law using his A and B coefficients in his 1917 paper. My question is, is it possible to separate the Planck radiation spectrum into a fraction that is spontaneous...
  21. C

    I Assumptions for blackbody spectra vs. emission spectra vs. absorption spectra

    Hi there, I am a physical oceanographer teaching an introductory undergraduate Earth science class that has a unit on astronomy. I have a physics undergraduate background, took a few astronomy classes at the undergraduate level back in the day, and did a bit of undergraduate research in...
  22. N

    B Do emission nebula glow because of ionised or excited electrons?

    I'm trying to figure out why emission nebulae glow. I read various sites such as a NASA website explaining why they shine; 'The massive stars embedded within the nebula give off enormous amounts of ultraviolet radiation, ionizing the gas and causing it to shine.' The Britanica article on...
  23. F

    De-excitation of a moving atom with photon emission

    The information I have are the following: ##p^\mu=(E, p, 0, 0)## ##p'^\mu=(E', p'\cos\beta, -p'\sin\beta,0)## ##k^\mu=\tilde{E}(1, \cos\alpha, \sin\alpha, 0)## Where: ##E=\sqrt{M^2+p^2}## ##E'=\sqrt{m^2+p'^2}## Using the conservation of the four-momentum ##p^\mu=p'^\mu+k^\mu##...
  24. muissi97

    Chemistry Emission Spectrum of an element

    The difference in energy between these two lines is that in the ultraviolet spectrum line, there is more energy because it has a shorter wavelength compared to the visible spectrum line as shown in figure 1.1 According to the Niels Bohr's model of the atom(figure 1.7) and figure 1.1, the least...
  25. Petr Matas

    B Prevalence of nuclear decays accompanied by gamma emission

    Some alpha or beta decays produce an excited daughter nucleus, which typically immediately emits one or more gama rays to reach a ground state. This is the case for beta decay of Co-60 or Na-24 for example. While the table of cobalt isotopes on Wikipedia mentions the gamma emission, the one for...
  26. P

    I Why are emission spectra of stars rarely shown?

    According to this link you just have to anlayse the light that isn't coming from a place on the star that has a light the source directly behind it e.g wouldn't looking at light from the outer edge of star give you an emission spectrum? http://www.thestargarden.co.uk/Spectral-lines.html
  27. K

    I Stimulated emission in harmonic oscillator

    Hello! Is stimulated emission possible for a harmonic oscillator (HO) i.e. you send a quanta of light at the right energy, and you end up with 2 quantas and the HO one energy level lower (as you would have in a 2 level system, like an atom)?
  28. K

    I Confused about spontaneous emission

    Hello! I thought that in spontaneous emission (say for an atom with 2 energy levels) we have the electron in the excited state and then it decays to the ground state emitting a photon at the resonance frequency. However I saw the attached figure, which introduces Mollow triplet. I understand the...
  29. I

    I Relation between blackbody radiation and spontaneous emission

    I'm wondering what the relationship between blackbody radiation and spontaneous emission is. As far as I know, there are three sources of EM radiation - thermal radiation, oscillating dipole (multipole?), and LASER. And it seems like light emission from an atom can be separated into two...
  30. R

    I Qualitative description of stimulated emission & population inversion

    I'm having trouble understanding stimulated emission and population inversion, and how they work together to make a laser work. I pretty much need this explained completely. 1. Spontaneous emission, they say, is when an atom absorbs and then later emits a photon. Isn't that just regular...
  31. Gabrielmonteiro

    I On the Rydberg Constant and the Emission Lines

    With regard to Rutherford's atomic model, and Rydberg's discovery in general for the hydrogen distribution lines, what does Rydberg's constant physically mean? Its unit is m ^ -1, as if it were a rate, but it was not clear to me its physical meaning. And why does it grow with atomic mass...
  32. R

    I How does this experimental result show photon emission?

    First I'll explain my understanding, because I'm not very confident in it. The main point is that the electrons are ejected and then accelerated to a very high kinetic energy. Then they start smashing into the anode. Most will go through a series of collisions before completely stopping, so that...
  33. M

    B Redshifted Photon Emission vs Transport: Magnitude of Gravitational Redshift

    I am considering the magnitude of the gravitational redshift and I look at the process of a photon leaving an atom from the Sun. I am asking whether the processes in the atom, viewed as a clock, would lead us to conclude that the emitted photon, at the time of emission, would itself be...
  34. F

    Electron-positron annihilation, photon emission angle

    I consider the laboratory system. The four momentums in this reference system are respectively: ##p^\mu = \big(\sqrt{|p|^2+m^2}, 0, 0, |p| \big)## ##p'^\mu= \big(m, 0, 0, 0 \big)## ##k^\mu = E\big(1, 0, 1, 0\big)## ##k'^\mu = E'\big(1, 0, -\sin \varphi, \cos \varphi \big)## I used conservation...
  35. J

    I Are all processes CPT symmetric like measurement, stimulated emission?

    https://en.wikipedia.org/wiki/CPT_symmetry says "CPT theorem says that CPT symmetry holds for all physical phenomena" - e.g. we could imagine decomposition of given phenomena into Feynman diagrams and apply CPT symmetry to all of them. However, for some o processes such reversibility seems...
  36. T

    1420 MHz--- the emission frequency of cold hydrogen gas

    I recently finished reading Paul Davies book The Eerie Silence, which is a book about the SETI (Search for ExtraTerrestrial Intelligence) project. In The Eerie Silence, Davies says that scientists using radio telescopes to search for radio messages from space aliens set their radio telescopes...
  37. dykuma

    A mathematical description of the physics behind Aurora?

    Maybe a bit of an odd question (not really sure where it would belong on this site to be honest), but I was wondering if anyone can explain, or at least knows of a source that explains in a quantitative way, the physics behind aurora? Now I've seen websites like this that discuss conceptually...
  38. P

    B 1-photon emission possible from electron-positron annihilation?

    I was reading about electron-positron annihilation. Typically it results in two photons, each with an energy of 511 keV, that go shooting out in opposite directions. But I read that in some instances three photons can result. Electrons have an intrinsic spin of ½, while photons have a spin of 1...
  39. M

    Photon emission in electronic transitions

    How would you explain, on a basic level, why only one photon (as opposed to two, three...) is emitted when an electron in an atom changes its energy level? This is for students with only introductory Physics background.
  40. AN630078

    Hydrogen Emission Spectrum and Electron Energy Levels

    1. The 4th line from the left, being the aqua blue line, corresponds to a wavelength of 486 nm, as blue light has a wavelength in the range 450-495 nm. 2. This is where I am having the most difficulty, I have tried to answer the question comprehensively but I am not satisfied with my answer. In...
  41. dRic2

    I How to read this decay sheet (gamma emission after beta decay)

    I was looking at the decay scheme (https://www-nds.iaea.org/relnsd/vcharthtml/VChartHTML.html) of ##^{112}Ag## which ##\beta##-decays to ##^{112}Cd##. ##Cd## is most likely left in an excited states, so it decays to its ground state by ##\gamma##-emission. As you can see there are tons of...
  42. K

    B Can spontaneous emission be considered a thermodynamic process?

    I realize that nothing causes an excited atom to emit a photon, and that it's a random process. But someone was asking me about why energized systems in general tend to lose their energy to the environment and move toward equilibrium. I mentioned that an inflated balloon, given a hole, will tend...
  43. Kayla Martin

    Optical depth using Bremsstahlung emission coefficient

    Equations I think may be relevant:
  44. K

    I The life cycle of a star and the bell shaped energy emission curve

    Do all stars in their life cycle (t) emit energy (E) that follow a bell shape curve? If yes, is the curve symmetrical always? How is this related to nuclear and thermal time scale?
  45. O

    B Emission from a coated cathode and tunneling

    I am wondering about an exercise exam question (it isn't homework): "at low temperatures (<2000 K), thermionic emission of a tungsten cathode depends on tunneling. By coating the tungsten with a suitable substance, the emission by tunneling can be greatly increased. Question: which two...
  46. F

    I How can a photon "stimulate emission" if it really does (Einstein coefficients)

    Einstein coefficients tell us that there is some probability for an atom to go from E_1 to E_2 given by the coefficient of absorption. This is fine, but why is there only one coefficient (absorption) going from E_1 to E_2 and two for the transition E_2 to E_1? Spontaneous emission makes sense...
  47. Erik Ayer

    I Polarization and Stimulated Emission

    If a laser beam has a definite diagonal polarization, it is in a superposition of horizontal and vertical polarization. If that beam were then sent through another lasing medium and caused stimulated emission of another photon (or possibly several photons), would those be in superposition...
  48. 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...
  49. Haynes Kwon

    I Absorption lines and emission lines in stellar spectra

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

    I Thermal photons emission inside a material

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