Wednesday, March 20, 2019

Curious about the chemistry of Carbon-14 after it's produced in the atmosphere


It's often explained how X14X2142C is formed in the upper atmosphere, a neutron hits a nitrogen atom and ejects a proton. Source. Since this is likely to happen to an NX2, I'm curious what the chemistry that follows is.


Does the energy of impact split the molecule, leaving a lone X14X2142C and a lone X14X2142N (and a lone hydrogen), (each highly eager to bond with something) or does it leave a CN which might also readily bond with OX2 or maybe something else. I'm mostly curious what the immediate chemical reactions are after the X14X2142C forms cause it seems to me that it should be initially pretty reactive.


Edit & maybe a partial answer:



It occurs to me after giving it some thought that if an NX2 is split into a free C and a free N, each would be most likely to bond to an OX2, or a single O from OX3 if the split happens near the ozone layer (which is possible given the listed height where most X14X2142C forms, "altitudes of 9 to 15 km" - same link as above). Initially I was thinking it might be more exotic than that, but having given this some thought I think that's what happens. The C and the N split and mostly each binds with OX2, 2nd most common they bind with O. CN is probably pretty uncommon, now that I think about it.



Answer



wikipedia article cites: "After production in the upper atmosphere, the carbon-14 atoms react rapidly to form mostly (about 93%) 14CO (carbon monoxide), which subsequently oxidizes at a slower rate to form 14CO2, radioactive carbon dioxide. The gas mixes rapidly and becomes evenly distributed throughout the atmosphere (the mixing timescale in the order of weeks)."


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