Notices
Results 1 to 6 of 6

Thread: Hydrogen spectrum

  1. #1 Hydrogen spectrum 
    New Member
    Join Date
    Jan 2009
    Posts
    3
    can we find Balmer, Paschen, Brackett, Pfund series in absorption spectrum of hydrogen? If yes, how? and if no why?


    Reply With Quote  
     

  2.  
     

  3. #2  
    Forum Junior c186282's Avatar
    Join Date
    Dec 2008
    Posts
    208
    Atoms will absorb and re-radiate at their resonate frequencies. The lines you talk about are just named sets of resonate frequencies for Hydrogen.

    Therefore if you have a gas of excited atoms. Like a gas of Hydrogen atoms with an electrical current running through the gas, then the atoms will spontaneously emit radiation at the atom's resonate frequencies. This light will be radiated in random directions.

    If you have a gas in it's ground state that is being back lit with light that contains frequencies that match the resonate frequencies of the atom, then the atoms will absorb some of the light. These atoms will then re-radiate in a random direction. Therefore the light that was absorbed and re-radiated will most likely not be traveling in the same direction as the rest of the light that is just passing through the gas. Therefore the observer will see a dark line in the spectrum of the light passing through the gas. This is called the absorption spectra.


    Reply With Quote  
     

  4. #3 Hydrogen spectrum 
    New Member
    Join Date
    Jan 2009
    Posts
    3
    Thanks for responding. But u didn't mention anywhere 'yes' or 'no'!!! A reference suggests that while giving an absorption spectrum, all the transitions must end to the n=1 state of hydrogen. Hence, giving only Lyman series in UV region. I want to check authenticity of the same, since many references talk about the presence of all series in its absorption spectrum (analogous to its emission spectrum), and reasonably I find that it MIGHT be true. Better to be sure only if u have experimented the same. If not, forward it to others. Hoping for reply.
    Reply With Quote  
     

  5. #4  
    Moderator Moderator Dishmaster's Avatar
    Join Date
    Apr 2008
    Location
    Heidelberg, Germany
    Posts
    1,624
    Maybe you should have a look at this website:
    http://outreach.atnf.csiro.au/educat...tro_types.html

    Balmer lines are observed in the optical range of the EM spectrum. They are a key ingredient to characterise stars in astronomy. Such spectra exist since the early 20th century. They are called , , etc. Here is a modern example:

    The line is also one of the most intense spectral lines in emission nebulae, because it is strongly populated in the cascade of recombinations in ionised gas. All the other hydrogen series are observed in the red or near IR range. Here they are called (etc.), (etc.) and so forth.

    Reply With Quote  
     

  6. #5 Hydrogen spectrum 
    New Member
    Join Date
    Jan 2009
    Posts
    3
    Thanx 4 giving actual photograph of Balmer absorption lines. Now i m convinced. I hope that the same is true 4 Paschen, Brackett & Pfund series in IR region. If not, let me know. I m a student of spectroscopy & since u r a 'dishmaster', I hope u'd know about baseline interferometry & aperture synthesis etc. Do u know about VLA ? Would u like to share info about it?
    Reply With Quote  
     

  7. #6  
    Moderator Moderator Dishmaster's Avatar
    Join Date
    Apr 2008
    Location
    Heidelberg, Germany
    Posts
    1,624
    First of all, you will notice the labels in the second and third image, where you find "P" (Paschen) ,"Br" (Brackett) and "Pf" (Pfund).

    Baseline interferometery is a complicated thing that needs some study (typically lectures during a semester) and cannot be explained in a single post here. You may want to play around with a virtual interferometer provided by a Java application at this website:
    http://www.narrabri.atnf.csiro.au/astronomy/vri.html

    I have worked at a single dish telescope (my avatar) for a few years and observed with a radio interferometer. I will try to find some references and let you know.
    Reply With Quote  
     

Bookmarks
Bookmarks
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •