Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Single photon emissions

  1. Mar 23, 2012 #1
    Why is it that for the H-atom there is no single photon emission in the transition from 2s to 1s? I realize that two-photon emission is valid in this transition but why not single-photon emission?
  2. jcsd
  3. Mar 23, 2012 #2


    User Avatar
    Science Advisor

    You need to obey conservation laws. For single photon optical transitions you need [itex]\Delta l=\pm 1[/itex] which corresponds to conservation of angular momentum. As a photon always carries angular momentum (it is a spin 1 particle), the angular momentum of the atom inquestion must change accordingly and only those transitions which fulfill this condition can be dipole-allowed.
    Last edited: Mar 23, 2012
  4. Mar 23, 2012 #3
    Ahh, that makes much more sense. Thank you!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook