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Two hydrogen atom with same spin can form H_2?

  1. Nov 29, 2011 #1
    As I know from the laws of chemistry,to form H_2 the H atoms must have opposite spin.
    What if they have the same spin?
    I mean, can an H atom rotate to swap his spin (i'm not expert of the dynamics of spin), or there is no way to couple them?
    In the case I have a gas of H with all of them polarized in the same direction is the formation of H_2 possible?
  2. jcsd
  3. Nov 29, 2011 #2


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    I believe that para-hydrogen has opposite spin, but ortho-hydrogen has matching spin.

    Para-hydrogen is spin 1/2, but I believe ortho-hydrogen is allowed 3 states of spin and is a spin 1 particle.

    Sorry, but I do not have a good reference on this at the moment, only memory.
  4. Nov 29, 2011 #3
    Oh so you talk about the spin of the proton, that's another interesting subject about coupling.
    I expressed myself badly, i was asking about spin of ELECTRON (i supposed chemists don't work with nuclear spin)
  5. Nov 29, 2011 #4


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    I wish I could find a handy reference, but the electrons for parahydrogen are always opposite, but the electons for ortho hydrogen can be both up, both down or opposite.

    The protons for parahydrogen are always opposite, and the protons for orthohydrogen are always the same.

    Does anyone have a reference to check...
  6. Nov 29, 2011 #5
    apparently not, provided that is you arrange for all the atoms to be polarized in the same direction by application of a high magnetic field at low temperatures.

    sadly however all i know about the subject is what i have gleaned from googling "spin polarized atomic hydrogen" an interesting question though!
  7. Nov 29, 2011 #6
    That's interesting. You'd then have H_1 with chemical properties that might be totally different then the familiar hydrogen. It would be half as dense, right?
  8. Nov 29, 2011 #7
    In my opinion, if the two atoms are polarized having the same spin, they must not form the H2 which means the covalent bond can not be formed. And the interactions between the same spin will be similar to the source of van der waals force which contains dispersion force, inducing force,orientation force. Just for the atoms having the same spin, i think only the dispersion force and inducing force will work.
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