Imagine that we have got some vessel under standard temperature and pressure filled with atomic Hydrogen inside and the electrons of these atoms have got the same spin and therefore they cannot join into Hydrogen molecules, so the process of recombination does not occur. But I was told that due to atoms’ collision to each other the spin of some electrons will be “overturned” and therefore the recombination will still occur slowly. Could you please tell me how to calculate the amount of time needed for complete recombination? That is when there will be no atoms of Hydrogen but molecules only. What this time depend on? On pressure inside the vessel? Temperature? Something else?