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Atomic Disguise Makes Helium Look Like Hydrogen
An anonymous reader writes "In a feat of modern-day alchemy, atom tinkerers have fooled hydrogen atoms into accepting a helium atom as one of their own, reports New Scientist. Donald Fleming of the University of British Columbia in Vancouver, Canada, and colleagues managed to disguise a helium atom as a hydrogen atom by replacing one of its orbiting electrons with a muon, which is far heavier than an electron. The camouflaged atom behaves chemically like hydrogen, but has four times the mass of normal hydrogen, allowing predictions for how atomic mass affects reaction rates to be put to the test."
This is super cool, but less for the kinetic isotope effect (KIE) studies and more for the muon-electron substitution. We've compared isotope masses with reaction rates using deuterium and tritium before, so using "H-4" and "H-5" is nice for extended validation, but not unexpected. The muonium is pretty bad-ass, though.
If you want a vision of the future, imagine a youtube comments section scrolling - forever.
does it make your voice go higher or lower when inhaled?
I come in last night about half past ten,
That hydrogen wouldn't let me in.
So muon on over. Rock it on over.
Move over little atom, a mean, old atom's muon in.
Program Intellivision!
There's no helium shortage. There's shitloads of it over there *waves in direction of Jupiter*
Fleming's team shot muons produced at the TRIUMF accelerator in Vancouver into a cloud of helium, molecular hydrogen and ammonia. The helium atoms captured the muons, then pulled hydrogen atoms away from the molecular hydrogen and bonded with them.
This was all done at TRIUMF, the world's largest cyclotron and by far the best particle accelerator in Canada. Plus, Donald Truhlar (a giant in the field) supported the experimental rate constants with quantum mechanical predictions - very neat stuff indeed!
Hey mate, spare a sig?
Yeah, like this. Sorry I didn't see your post. My Ph.D. advisor, Larry Biedenharn, was heavily involved in this for four or five years, but as I said, it didn't quite pan out partly because of the sticking problem, partly because one can only make muons at something like 10% energy efficiency (remembering from the many seminars we had on this back in those days, not looking up the exact numbers). Larry always thought they'd do it with a special "breeder" fission reactor to get the muons for free as a side-effect of making energy the other way to boost fission returns by a factor of 50% or so, but this never happened AFAIK.
It is still an open problem -- the question is really is there an environment where the He sticking problem is suppressed (they didn't find one, but I doubt the search was exhaustive) and is there any way to produce muons at higher efficiencies -- say some sort of resonant conversion of electrons into muons that beats 5-10%. My recollection is that they were within a factor of ten, maybe even within a factor of 2-3 of break even but couldn't quite find a way over the hump. They know way more about neutrinos now than they did back then -- one wonders if anybody is even thinking about it any more.
rgb
Even when the experts all agree, they may well be mistaken. --- Bertrand Russell.
The atom has no physical shape. If the p1 orbital occupied by the single electron is similar enough "chemically", the effective radius will also be identical.