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Antimatter Atoms Captured
Whamo writes: "Researchers at CERN think they have created and stored thousands of antiatoms in a particle trap. The researchers first used powerful magnetic fields to trap antiprotons then exposed this to a beam of positrons. Initial results indicate that at least some of the antiparticles have bound together to become neutral antihydrogen atoms. How cool is that?"
The theory goes that anti-hyrdogen should have all the same observable physical properties that hydrogen does. If we can start to manufacturer and store non-trivial quantities of the stuff we can actually start to test whether or not this is true. We can see if it has the same obsorbtion spectrum as hydrogen, the same atomic weight, etc...
If there is a difference we might be able to use it to confirm or disprove our assumption that the entire universe is made of 'normal' matter. For example, if there is an observable difference between the absorbtion spectra of hydrogen and anti-hydrogen, we'd have a test to determine if a distant galaxy was made of anti-matter. If there is no difference, well, we've found a very expensive way to heat a small cup of coffee.
-josh
So how do you keep a neutral particle in an electromagnetic field? Ionize it, and it's just an antiproton, again. It would seem to me that the lightest *anti-atom* you could keep in an electromagnetic field would be singly-ionized antihelium. (After all, doubly-ionized antihelium is just an anti-alpha particle, or is that alpha anti-particle?)
The living have better things to do than to continue hating the dead.
Chris :
I think both of the tests you mention are not really confirmation of the fact that they have actually formed anti-hydrogen.
Why? Let's assume that, for some reason, the atoms in question were not anti-hydrogen, but simply plain run-of-the-mill hydrogen.
How do the spectra compare? The spectrum of hydrogen should be exactly identical to that of anti-hydrogen. Nope. Can't use it as a confirmation of the antimatter state.
How about net charge? Well, hydrogen also has zero charge. Nope, can't use net charge as a confirmation either.
In fact, your argument is not quite correct. Hydrogen atoms do possess a net magnetic moment (primarily due to the spin and orbital angular momentum of the electron, though the latter is zero in the ground state) and therefore do move in a magnetic field. In fact, that was the entire basis of the classic Stern-Gerlach experiment.
I've heard that experimentalists might be able to confirm the existence of anti-hydrogen by smashing the atoms in question against a wall, and looking for characteristic gamma rays. If one knew the initial state were either hydrogen or anti-hydrogen, then one could be assured upon seeing the gamma rays, that the initial state was indeed anti-hydrogen. The problem with this approach is that it destroys the antimatter atoms in the process, so that you are not able to subsequently use them in other experiments.
Bob
Science, like Nature, must also be tamed, with a view turned towards its preservation.