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Ratio of positive to negative hydrogen ions in the universe?

  1. Jan 21, 2014 #1
    Hi this may sound like a simple question but I'm trying to find out the relative abundance of hydrogen in its various forms in space:

    H, H+, H-, H2, H2+, H2-

    I'd like to know these for our stellar neighborhood involving the solar wind and also for interstellar space outside the heliopause.

    I was hoping to use the energy required to remove an electron from hydrogen vs. the energy to add an additional one. I looked at ionization energy but it's been too long since I studied it in school. I was wondering if the Bohr model might work for this simple case:


    * Could someone direct me to a table showing the energy required to add or remove an electron from H to create H- (hydride) and H+ (hydron), or are they identical?
    * The same for H2 to H2- and H2+
    * Does someone know the ratio of H to H2 in the universe?

    Perhaps from there we can make a good guess as to the relative abundances. I also would like to find these ratios for helium but it's not as critical (I'm studying aspects of the Bussard ramjet and Zubrin solar brake and how much would be lost to some ions going the opposite direction).
  2. jcsd
  3. Jan 22, 2014 #2
    I did a bit more research and found that even though space is cold, its pressure and density are so low that it's filled with a high temperature plasma, which means that mostly the hydrogen protons are separated from their electrons:


    https://en.wikipedia.org/wiki/Trihydrogen_cation (perhaps most abundant ion)

    So cosmic rays keep the plasma separated which creates H2+ and that quickly combines with H2 to create H3+ and H. There is evidently little H+ at any pressure. But I don't know how often some of the free electrons combine with protons to create H2- (and probably H3- and almost no H-). I still can't find relative concentrations of the hydrogen molecules and their positive ions.
    Last edited: Jan 22, 2014
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