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

What is self and air broadening effects?

  1. Apr 20, 2010 #1
    What is self and air broadening effects? I have read that they appear in atmospheric modelling. Is this pressure broadening?
     
  2. jcsd
  3. Apr 21, 2010 #2

    sylas

    User Avatar
    Science Advisor

    Re: Broadening

    There is a "broadening" in spectral lines of emission of radiation from a gas. This is quite important for remote sensing by satellites with microwave sounders, and also for modeling how radiation interacts with the atmosphere. It is also relevant to study of emission lines in the spectrum from a dense plasma, such as the atmosphere of a star.

    For problems relating to how thermal radiation interacts with an atmosphere, the relevant effect is called "pressure broadening" or "collisional broadening"; the collisions between atoms in a dense gas can alter the energy of radiation emission, which broadens the corresponding spectral line. It's a rather horribly complicated effect to model accurately; in fact I understand there is no exact theory to describe the broadening effects of pressure on spectral lines; although there are adequate heuristic descriptions.

    Wikipedia gives a brief summary of the kinds of broadening of spectral lines that can occur; and this may help give pointer to where to find more detail from more technical sources of information. See Spectral line broadening and shift within the wikipedia article on "Spectral Line".

    A good discussion is also available in A First Course In Atmospheric Radiation, by Grant W. Petty (Published 2006, Sundog publishing). The link goes to a webpage for the book and you can browse the first edition for free. Pressure broadening and doppler broadening are discussed in chapter 9.

    Cheers -- sylas
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: What is self and air broadening effects?
  1. Cold Air (Replies: 53)

  2. Viscosity of air (Replies: 3)

Loading...