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. K

    Does Einsteins coefficient for spontaneous emission depend on energy difference?

    Hi.. Does the Einstein's coefficient for spontaneous emission B depend upon the energy difference between the two levels?
  2. C

    Positron Emission: Exploring the Science Behind It

    I've been wondering about positron emission. If a neutron has more mass than a proton, how can a proton turn into a neutron by releasing a particle with mass? [PLAIN]http://img37.imageshack.us/img37/654/positronemission.gif (source:http://en.wikipedia.org/wiki/Positron_emission) Doesn't this...
  3. B

    Emission spectral line intensity

    Dear all I need to calculate the intensity of the spectral line. I have data from NIST website: wavelength, Aki (Einstein coefficient), gi, gk, Ei and Ek energy levels. How do i go about Thanks for your help
  4. F

    Emission spectrum for Helium

    Homework Statement The numbers following are the results of a lab experiment to find the spectral lines of Helium in a gas discharge tube. The lines I got were roughly: 703nm, 660nm, 590nm, 500nm, 490nm, 470nm, 450nm. The question is, what possible electron transitions could the...
  5. F

    Wavelength, emission spectrum, electron transitions

    Homework Statement Determine the wavelength (in nm, to one decimal place) of the line in the emission spectrum of the He+ ion produced by a transition from n = 3 to n = 1. Homework Equations I used the Rydberg equation for this, although I'm not sure it is the correct one to use...
  6. H

    Super Novae and emission of electromagnetic waves and gravitation wavefronts

    Hello, could you please help to clarifly the following. Do electromagnetic (e.g. light) and gravitational wavefronts caused by e.g. a supernova both appear at the same time seen from a distant observer perspective? Thank you!
  7. snoopies622

    Photon emission from simple harmonic oscillator

    I've looked at a few introductory treatments of the quantum harmonic oscillator and they all show how one arrives at the discrete energy values E_n = ( \frac {1}{2} + n ) hf \hspace {10 mm} n=0,1,2... usually by setting up and then solving the Schrodinger equation for the system...
  8. O

    X-Ray Emission from Synchrotrons vs. Cyclotrons

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  9. C

    Emission Spectrum - Does Energy Always Transfer in Photon Form?

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  10. A

    Exploring Light Emission and Newtonian Physics

    From what I have learned so far, it appears that a light emission orthogonal to motion acts exactly like a Newtonian massive particle with conserved longitudinal momentum. Is this correct? If so it would seem to be a cosmic coincidence of monumental proportions. Having given it some...
  11. I

    Absorption & Emission: What Causes Electrons to Excite?

    I seem to have some trouble finding a definite answer by searching the following: It is my understanding that when an electron is excited to a higher energy state, it will spontaneously decay back and emit a photon. My questions are: Is the wavelength of light required to excite an...
  12. J

    Why Does Alpha Emission Occur in Nuclear Physics?

    Hi, quick one: In my nuclear physics notes it says alpha emission is often the only light particle emission that takes place due to its very high binding energy. What I don't understand is that how come the nucleus wants to retain binding energy? I would have thought that it wants to get...
  13. M

    What's the difference between emission and absorption?

    My textbook says "absorption yields color. emission yields fluorescence" - can someone explain what that means exactly. I know color is when something absorbs all wavelengths except one, which gets reflected and produces color. If it helps... the chapter is on bohr's model.
  14. J

    X-rays and their emission spectrum

    About the intensity of x-ray emission spectrum of Molybdenum as a function of wavelength for various applied voltages: Explain fully: 1) the production of continuous radiation emitted 2) the absence of radiation of wavelength shorter than the minimum wavelength 3) the presence of the...
  15. T

    What's the hard bremsstrahlung emission?

    Hi! I need to know what's the "hard bremsstrahlung emission". I googled it but it only showed papers (and few because my university don't have access to many) on experiences that at some point mention this effect but don't explain it. I know what's bremsstrahlung emission, just don't know...
  16. P

    Termoelectric Emission: Measuring T & I_A for Work

    I_A=BT^2e^{-\frac{e\varphi}{k_BT}} We measure T and I_A and from that get work. If T_0 is first temperature in which we measured than we get \frac{I_A}{I_{A0}}=\frac{T^2}{T^2_0}e^{-\frac{e\varphi}{k_BT}(\frac{1}{T}-\frac{1}{T_0})} And from that we get...
  17. M

    Slit diffraction: time between emission and detection of photon

    For this question I am considering a slit diffraction experiment set up as follows: {Monochromatic source} ------> {Single slit} ------> {Diffraction grating with N slits} ------> {Screen with small movable detector} The monochromatic light source emits photons one at a time. The principal...
  18. A

    Calculating Wavelength Using Atomic Emission Spectra and Balmer Series Equation

    in an experiment we looked through the diffraction grating to see the spectrum made by a helium lamp. we measured the distance along the meter stick to the point where we saw each color. based on that distance how would you calculate the wavelength of the light that was seen? would you...
  19. D

    Calculating Gamma Ray Emission Recoil Speed

    Homework Statement A 67-Zn nucleus is at rest and in its first excited state, 93.3 keV above the ground state. The nucleus then decays to the ground state with the emission of a gamma ray. (One atomic mass unit is 931.5 MeV/c2.) What is the recoil speed of the nucleus? (You can assume...
  20. T

    Emission probability calculation (quick and easy question)

    Hi! This is a very basic question. How do I calculate the total probability for a certain gamma of a decay? For example, I know from empiric method that the 2 gammas from Co60 have a probability of 50%. But for Eu152 I have lots of gammas and I need to compute them all in a simulation program...
  21. B

    Child's Law and Thermionic Emission

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  22. T

    Emission in hydrogen atom - difference between electrons and photons

    A gas composed of hydrogen atoms in the ground state is bombarded with electrons of energy 12.5eV. a) What wavelengths emitted can we expect to observe? b) If we replaced the incident electrons with incident photons of the same energy, what would happen? I know the answers to both...
  23. rhody

    Exploring the Mysteries of Cryogenic Electron Emission

    Physics.org: March 10, 2010 By Lisa Zyga Hans-Otto Meyer, a physics professor at Indiana University has shown that the electron firings are distributed in time, in burst patterns, but in a "peculiar, correlated way", he believes the correlation involves some kind of trapping...
  24. P

    Emission Spectra of Elements: List & Resources

    I was just wondering if anyone knew of anywhere on the internet that had a list of all known emission spectrums of the elements. Thanks!
  25. S

    Proving 8Be Ground State Stability vs Nucleon Emission

    Homework Statement The question is longer than this but the part I'm stuck on is this - Show that the ground state of 8Be is stable against nucleon emission. Homework Equations I'm not sure which ones to use... I used the binding energy formula. The Attempt at a Solution what I'm...
  26. V

    Gas Laser: Stimulated Emission and Positive Ions

    In a gas laser, an electron in the highest energy state absorbs photon for stimulated emission to occur, but now since it has more energy than its highest state, shouldn't it escape the atom and the active medium be left only with positive ions?
  27. Johnny_Sparx

    Help finding electric field for phonon emission.

    Hello, I seem to be having a problem with an assignment :confused: : I need to calculate the electric field at which optical phonons will be emitted. Here's what I have been given: Semiconductor with effective mass m=0.26*m0. The optical phonon energy is 50 meV. The mean scattering time...
  28. A

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  29. L

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  30. H

    Radioactive Emission: Determining Half-Life

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  31. S

    Question on emission of electrons

    Homework Statement Monochromatic light of wavelength 4.5 x 10-7 m will eject electrons from the surface of a metal with a maximum KE of 3.2 x 10-19 Joules. Will light having a wavelength of 6.8 x 10-7 m also cause emission of electrons from this metal Homework Equations E = h.c/lambda...
  32. B

    New Pulsar Emission Mechanism?

    In papers presented this week to the American Astronomical Society, Andrea Schmidt and John Singleton of Los Alamos National Laboratory provide detailed analyses of several pieces of observational data that suggest that pulsars emit the electromagnetic equivalent of the well-known "sonic boom"...
  33. W

    How are emission spectra of gases affected by being in water?

    Happy New Year to all you Physics Geniuses out there! I have a question concerning how the optical emission spectrum of a gas would be affected by being dissolved in water. I know very little about spectroscopy so please forgive me if this seems like an idiotic question. Let's assume I...
  34. deccard

    Emission in hydrogen atom: recoil and photon properties

    I have been trying to picture the whole process of a photon emission by a atom. So to have good understanding what is going on, I have came up with following experimental setup. A single hydrogen atom in excited state ^2\!P_{1/2}, which has been orientated with a magnetic field so that...
  35. I

    What Temperature is Needed for Hydrogen Gas to Produce a 656.2nm Emission Line?

    the question states that the emission spectrum of hydrogen contains a line with wavelength 656.2nm. and we need to approx find out what temp the H gas needs to have to be heated before this line appers in the spectrum i have worked out that for this wavelength the electron mov from level 3 to...
  36. T

    What is the Earth's emission spectrum as seen from outer space?

    Hello, Does anybody know if there has ever been an emission spectrum of Earth recorded by one of our spacecraft s after launch from outer space? When we directly image extrasolar planets we are able to determine their atmospheric properties, etc, so can someone point me to a link which...
  37. K

    Planetary Nebulae and emission lines

    Homework Statement A planetary nebula is larger when imaged in H\alpha than when observed in a Helium line, Why? Homework Equations The Attempt at a Solution I understand that a planetary Nebula gives an emission spectrum and that If the nebula looks larger in a H line there is...
  38. D

    Calculating Width of One-Dimensional Box for Photon Emission

    Homework Statement When a hydrogen atom undergoes a transition from the n=2 state to the n=1 level, a photon with \lambda=122nm is emitted. a)If the atom is modeled as an electron in a one-dimensional box, what is the width of the box in order for the n=2 to n=1 transition to correspond...
  39. K

    Photoelectric Emission: Kinetic Energy, Velocity, Frequency Explained

    It is known that for light of a given intensity when incident on a photoelectric material, the number of electrons emitted is independent of the frequency of light, but increases when the intensity of light goes up. However, the maximum kinetic energy of the emitted electrons increases with the...
  40. D

    Emission of infra red from hot bodies

    I've seen much mention in websites of matt black surfaces being better emitters of infra red than shiny silver ones so if a matt black and shiny silver surface are heated to about 100 deg C the black one will cool down more quickly as a result of this! Doesn't Wien's law state that the amount of...
  41. K

    Exploring Emission Spectra: Comparing Results for H, He, Ne, Hg, and N2

    Hey all, I have a lab coming up that deals with the emission spectra of H, He,Ne,Hg, and N_2 I am looking around for some sources to compare my results to, and I thought I would post here in case anyone knows of a good (preferably online) journal article or reputable website that would...
  42. M

    Radiation Emission Spectrums for Alpha, Beta, and Gamma

    Homework Statement I'm taking a nuclear physics seminar, and I'm wondering what causes the differences in the energy spectra between alpha, beta, and gamma emissions. Specifically, why is dispersion for energy values in alpha radiation so different from that of beta? I'm also looking for a...
  43. S

    Stimulated Emission: Why Are Photons In Phase?

    Hi. I can't see why the photon created by stimulated emission in a common laser should be in phase and with the same polarization of the original photon. Thank you.
  44. E

    Emission Spectra: which electrons?

    I am a newbie to the forum and impressed by the breadth and depth of the material here. After searching I am unable to answer a question that I have been pondering. One of my brightest students asked whether electrons other than the valence electrons were involved in the emission spectra of...
  45. H

    Emission and Absorption bands?

    I have been wondering lately, as I am quite new to physics. If an atom dropped from it's first energy level back to it's ground state, and emitted a photon. Could a photon of the same wavelength excite the atom back to it's first energy level? What is the difference between emission and...
  46. B

    Short question: Spontaneous emission from Feynman diagrams?

    Hey all, I am just wondering if one can directly calculate the Einstein coefficient in spontaneous emission of, say, two-level atoms through feynman diagrams? I searched for sources in google but could not find anything. Thanks a lot for an answer! Wit best regards, blue2script
  47. T

    How Does Recoil Affect Photon Emission and Absorption Frequencies?

    Homework Statement Show that the fractional change in frequency of a photon absorbed or emitted by an atom initially at rest is \frac{\nu - \nu_o}{\nu} = \pm \frac{h\nu}{2Mc^{2}} where M is the mass of the atom, \nu_o is the frequency of the transition uncorrected for the recoil of the atom. In...
  48. Z

    Absorption line spectra and emission line spectra

    Why don’t emission and absorption properties of an atom cancel out such that no such spectral lines are seen. If electrons in atoms are excited from level 1 to level 2 and absorb energy at some specific frequency, why don’t they then emit that same frequency when they fall back down to level1...
  49. S

    Stimulated Emission: Intuitive Explanation Needed

    I am trying to find an intuitive explanation for the stimulated emission phenomenon. I know the effect: a photon with the right frequency "interacts" with an excited electron to create a copy of itself( same phase, same amplitude, same state) putting the electron to a lower energy state... But...
  50. T

    Question on neutrino emission machanism in neutron star

    How many neutrino emission mechanism, that causes the cooling of star, are there in neutron star? And How, what equation, to calculate the emissivity of each mechanism? thankfully, First
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