Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Kryptid on 08/09/2006 05:01:01
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I've been trying to find a possible new combination of charged particles that will form a stable atom other than the proton-electron-neutron combination. However, all of the exotic atoms I know of are unstable (muonium, for example). But forget about that for now. I have a hypothetical question:
Assume that you have a cesium cation (or other cation), which of course, carries a positive charge. Then, an antiproton comes along and is attracted to the cesium cation because it is negatively charged. Here are one of four possible outcomes I've thought of:
(1) The antiproton enters the ion, and occupies the empty orbital where the valence electron is supposed to be. Thus, a neutral exotic atom is formed, which has both electrons and an antiproton orbiting the nucleus. In this instance, the antiproton occupies the valence orbital.
(2) The antiproton enters the atom, and "sinks" into the 1s orbital, because it is far more massive than the orbiting electrons. Thus, the electrons that once occupied the 1s orbital are displaced to higher orbitals. The same goes for all of other the electrons too. The result is a neutral exotic atom with an antiproton in the 1s shell instead of the valence shell (as with the possibility (1)).
(3) The antiproton behaves as if it were a tiny anion (being negatively charged), and forms an ionic bond with the cesium cation. On a large scale with many cesium cations and antiprotrons, the result may be a crystalline solid with an ordered lattice of cesium cations and antiprotons.
(4) The antiproton works its way through the cloud of electrons and collides with the cesium nucleus, annihilating with one of the nucleons, and thus destroying the atom. It's an undesirable event in my mind, but it also seems to be the most likely one.
If you don't think any of these events are the probable outcome, then please, tell what you think would happened. It would just intrigue me if one of the first three possibilities is the correct one, as it would allow for exotic chemistry as well as a potentially stable storage for antimatter.
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(1) is not possible because (as you say in (2)) the higher mass implies lower orbiting radius. If I remember correctly, orbiting radius is approximately inversely proportional to the negative particle's mass, so it should be ~ 2000 times less.
(2): probably, just because of the different mass from the electron one, the solution of Schrodinger equation for antiproton is different from that for electron, so 1s, 2s, 2p ... orbitals are not the same, in which case the antiproton with other electrons occupies completely different orbitals.
(3) I don't know, but the little antiproton's radius gives me the idea that this is difficult: the electric field in the antiproton proximity is very high.
(4) shouldn't happen if the antiproton's momentum is very low, because of electrons repulsion.
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The only reason the so electrons are mostly outside the neucleus is that there is no room for them in there they are too "big" because of their low mass they have no angular momentum and do spend some time inside the neucleus. Your antiproton would try to do the same thing with (of course) disastrous results.
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Over extended periods of time, the atom can go through a lot of changes. The strong force is sure to spell disaster for the proposed atom, but it might work for a few microseconds.
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I had the same question!!!
My initial thought was that the 54 electrons in Cs+ would be enough to keep the antiproton away (at least for a little while--Au+, Hg22+ or Tl+, with might be even better). It's possible that a perfect crystalline array might even be stable (if the electrostatic fields balance out right). I worry that the increased mass of the antiproton would naturally cause it to "want to" occupy an orbital that is very close to the nucleus. Additionally, the huge mass difference between it and an electron also means that the electrons may not actually have much stopping power--it's essentially the Born-Oppenheimer approximation--the electrons will be deflected much faster than the antiproton, and they will be deflected more. I am assuming that once the antiproton manages to get "inside" the 1s orbital it is as good as half a gamma ray.
If you did somehow manage to isolate a stable sample of antiprotons (doped into a CsI lattice or something), you would want to keep it dry!! Water would find its way into the crystal pretty quickly and act as a proton source. It would be a super-acid-base reaction!
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I heard that recent theoretical studies showed that it may be possible to improve the stability of "positronium" (an electron+positron orbiting each other) by shining a laser of the right frequency on them, so that they keep getting re-boosted into a higher orbit.
This might work for an isolated "atom" of positronium in a vacuum, but if you tried to store it as a dense crystal, the energy bands will broaden, and positrons may collide with adjacent electrons. Cryogenic cooling may help, but it would be difficult to maintain temperatures near absolute zero with gamma rays firing off all the time.
The same might be possible with isolated muonium (except that isolated muons are themselves unstable) or isolated proton+antiproton combinations. The energy required to boost the subatomic particle into a higher orbit increases with the mass of the particle: hundreds of times for a muon, thousands of times for protons.
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Forming a stable atom in this way is impossible because the anti-proton is attracted to the proton by both the electric field of the nucleus and the strong force. When the anti-proton comes in contact to a proton they will annihilate each other releasing radiation in the form of photons.
Note: The term exotic matter is often used to refer to matter which has a negative mass density, which is not the case here. A better term for what you're talking about would be exotic atoms. If exotic matter exits then it'd be possible to create a stable wormhole. See http://en.wikipedia.org/wiki/Exotic_matter