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Chemistry

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3
  • $\begingroup$ I guess this has something to do with nuclear spin. $\endgroup$
    – Ivan Neretin
    Commented Mar 16, 2017 at 15:29
  • 1
    $\begingroup$ @ Ivan Neretin ; yes nuclear spin seems to be is the cause, D has a spin of 1 whereas H has spin 1/2. In $\ce{H2}$ the ortho-para ratio is 3:1 but 2:1 in $\ce{D2}$ there is some detail here chemistry.stackexchange.com/questions/67316/… which you will have to modify for deuterium. $\endgroup$
    – porphyrin
    Commented Mar 16, 2017 at 16:25
  • $\begingroup$ also there is the fact that the rotational constant for deuterium is almost half that for hydrogen, $60.85 \pu{cm^{-1}}$, so many more rotational levels are occupied at a given temperature. $\endgroup$
    – porphyrin
    Commented Mar 23, 2017 at 16:21