[HN Gopher] Antiproton Orbiting Helium Ion
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Antiproton Orbiting Helium Ion
Author : hexo
Score : 120 points
Date : 2022-03-16 16:11 UTC (6 hours ago)
(HTM) web link (arstechnica.com)
(TXT) w3m dump (arstechnica.com)
| tlogan wrote:
| Question: would antiproton with antielectron orbiting around it
| be stable as normal hydrogen atom?
|
| Did somebody made an experiment like that?
| [deleted]
| Pulcinella wrote:
| Yes. It should be indefinitely stable as long as it does not
| come into contact with regular matter.
|
| https://en.m.wikipedia.org/wiki/Antihydrogen
| nuccy wrote:
| If antimatter was created during the Big Bang (and it was, we
| actually just don't know why there is more matter than
| antimatter [1]) it could exist in issolated-enough patches of
| the Universe. Photons, gravitational waves or neutrinos
| coming from those regions would not differ in any way, so we
| would not be able to identify those regions, up until they
| merge with normal-matter-filled ones (which is unlikely due
| to accelerated expansion of the Universe [2]).
|
| 1. https://home.cern/science/physics/matter-antimatter-
| asymmetr...
|
| 2. https://en.m.wikipedia.org/wiki/Accelerating_expansion_of_
| th...
|
| Edit: as a matter of fact experiments, like the one described
| in the posted paper, allows to shed some light on the
| properties of antimatter and why there is more matter in the
| Universe (matter-antimatter anisotropy).
| breuleux wrote:
| > it could exist in issolated-enough patches of the
| Universe. Photons, gravitational waves or neutrinos coming
| from those regions would not differ in any way, so we would
| not be able to identify those regions, up until they merge
| with normal-matter-filled ones
|
| Interesting. So how do we know there actually is more
| matter than antimatter in the universe? Couldn't there be a
| roughly equal number of sufficiently isolated pockets of
| each?
| Sharlin wrote:
| It is a well-known hypothesis, but space is not empty
| enough for it to be consistent with observations at least
| within our observable universe. If there really were
| antigalaxies or anticlusters out there, we would expect
| to observe characteristic gamma ray photons from the
| matter-antimatter boundaries where the extremely sparse
| but still existing intergalactic medium would interact
| and annihilate.
| jl6 wrote:
| What a bummer - to send an intergalactic probe to a far-off
| supercluster only to find it's made of antimatter and you
| cannot interact with it (if you survive the close encounter
| long enough to find this out).
| [deleted]
| lmilcin wrote:
| Yes and yes.
|
| As far as we know anti-atoms (antihydrogen in this case) are as
| stable as normal atoms.
|
| To the point where it creates interesting questions -- if
| antiatoms are exactly as normal atoms, why we have abundance of
| normal matter but not antimatter?
| starwind wrote:
| AFAIK, anti-hydrogen is very stable on its own and only gets
| annihilated because it quickly comes in contact with matter.
|
| > In November 2010, the ALPHA collaboration announced that they
| had trapped 38 antihydrogen atoms for a sixth of a second, the
| first confinement of neutral antimatter. In June 2011, they
| trapped 309 antihydrogen atoms, up to 3 simultaneously, for up
| to 1,000 seconds.
|
| https://en.wikipedia.org/wiki/Antihydrogen
| fasteddie31003 wrote:
| So could we make a rocket engine out of this? We would need to
| store antiprotons and then shoot them at helium, right?
| Robotbeat wrote:
| Muons can do something similar, and it has the effect of reducing
| the effective radius of the atom, which can catalyze fusion.
|
| Which makes me wonder... is antiproton catalyzed fusion a thing?
| Does the antiproton last long enough? Muons are inefficient to
| produce. Can antiprotons be made significantly more efficiently?
| marcosdumay wrote:
| > is antiproton catalyzed fusion a thing?
|
| I imagine on any geometry you can create the anti-proton will
| be absorbed by the nucleus much quicker than another nucleus
| can.
|
| On what is easier to produce, currently muons are much easier.
| ISL wrote:
| It is much more difficult to produce antiprotons than muons.
|
| Furthermore, my guess is that the proton-antiproton
| annihilation rate is much faster than the rate of antiproton-
| catalyzed fusion. Muon catalysis doesn't have the annihilation
| channel (the heavy negatively-charged particle is _always_
| close to one H /D/T nucleus), so it will catalyze fusions all
| day until it decays. The antiproton can simply annihilate.
|
| That said, antiprotons probably would catalyze fusion at some
| rate. Whether it is higher or lower than muon catalysis, I'm
| not sure. If the antiproton orbital radius is too small, it may
| actually lower the capture cross-section for a neighboring
| hydrogen, even if the post-capture fusion cross-section is
| (almost certainly) higher.
| ben_w wrote:
| I'm not sure about antiproton _catalyzed_ fusion, but I have
| heard of antiproton induced fission induced fusion:
| https://space.nss.org/wp-content/uploads/Space-Manufacturing...
| jesuslop wrote:
| Seems it'd have to be ultra-hot and ultra-cool at the same time
| kurthr wrote:
| Ok, now have a bosonic anti-alpha (two neutrons and two anti-
| protons) orbit in a He4 Bose Condensate!
| croddin wrote:
| This makes me wonder, if we had a significant amount of anti-
| hydrogen (but not enough to make a star), what would be the most
| complicated thing we could build out of it, and how would we go
| about doing so? (I also asked on:
| https://physics.stackexchange.com/questions/699258/building-...)
| amelius wrote:
| As fuel for a reactor? And just colliding it with normal
| matter, driving a steam engine would be enough.
| nynx wrote:
| I'm not sure what you mean by enough to make a star. Stars
| don't have antimatter in them.
| renewiltord wrote:
| One would expect a sufficiently large amount of antihydrogen
| to form an antistar.
| croddin wrote:
| I just mean that most elements besides hydrogen are made in
| stars, theoretically with a very large amount of hydrogen you
| could make an antimatter star, but without doing that, what
| elements, molecules etc would we be able to make, if we had
| access to a large amount of anti-hydrogen that was contained
| so that it would not annihilate with our matter.
| chasil wrote:
| Positive beta decay can and does happen, so while this
| assertion is correct for all intents and purposes, it is not
| strictly accurate.
|
| One of the potassium-40 decay paths is the emission of a
| positron, and this does happen in the human body. Stars with
| potassium-40 metalicity would see this beta decay as well.
|
| "Very rarely (0.001% of events), it decays to 40Ar by
| emitting a positron (b+) and a neutrino."
|
| https://en.wikipedia.org/wiki/Potassium-40
| amelius wrote:
| Looks like semiconductor physics is about to get more
| interesting. Now we have electrons, holes, and antiprotons ...
| AnimalMuppet wrote:
| You do _not_ want antiprotons in your semiconductors. They will
| orbit much more tightly than the electrons; there is nonzero
| overlap of their wavefunction with the protons in the nucleus.
| There will be interactions (annihilations), and those will
| _not_ be good for your semiconductor device.
| [deleted]
| londons_explore wrote:
| Could this lead to a storage mechanism for anti-protons?
| fsh wrote:
| Antiprotons can be stored pretty much indefinitely (many years)
| in cryogenic Penning traps. This is done by the BASE
| collaboration at CERN [1] who are actually neighbors of the
| group that the article is about.
|
| [1] https://base.web.cern.ch/
| ethbr0 wrote:
| CERN: the only place you can pop over to your neighbor to ask
| for a cup^H^H^Hstream of antiprotons.
| ISL wrote:
| I don't think they're presently operating the antiproton
| source, but for decades one could get them at Fermilab,
| too.
|
| https://www.fnal.gov/pub/tevatron/tevatron-operation.html
| amelius wrote:
| How close does an anti-proton have to come to a proton to become
| annihilated?
|
| And, when a ball of matter and anti-matter collide, will they
| completely annihilate, or will the initial impact blast them
| apart such that parts will stay intact? Does initial speed
| matter? Would we be able to partially annihilate a proton?
| hexo wrote:
| Antiparticles have oposite quantum numbers, so it means they
| also have oposite electric charge. Basicaly, they would attract
| as much as possible and, you know, kaboom. This is a compostite
| particle made of quarks, which under annihilation produce their
| gauge particles - gluons. These quickly undrego hadronization -
| will pair-up to produce mesons. These are unstable af so they
| decay. Ultimate fate is photons, electrons, positrons and
| neutrinos. Even, antiproton can annihilate with neutrons, which
| makes sense given similar internal structure. Keep in mind that
| during conversions energies are preserved. So that when lighter
| particles are produced, they move faster. So yes, it would be
| ripped apart, kind of.
| amelius wrote:
| > Antiparticles have oposite quantum numbers, so it means
| they also have oposite electric charge. Basicaly, they would
| attract as much as possible and, you know, kaboom.
|
| This is true, but an electron and nucleus also have opposite
| charge, yet the electron typically doesn't drop into the
| nucleus all the time.
| scrumbledober wrote:
| This seems like something that wouldn't even be written about in
| sci-fi books because it just doesn't make sense to ever be
| possible. It seems impossible to even imagine the implications.
|
| I also can't imagine future chemistry students needing to
| memorize two separate sets of electron and antiproton orbitals.
| Pulcinella wrote:
| Note that this isn't the first time these kind of "exotic"
| atoms have been created.
|
| https://en.m.wikipedia.org/wiki/Exotic_atom
| https://en.m.wikipedia.org/wiki/Antiprotonic_helium
| https://en.m.wikipedia.org/wiki/Antihydrogen
| gus_massa wrote:
| From Wikipedia:
| https://en.wikipedia.org/wiki/Antiprotonic_helium
|
| > _The antiproton can thus orbit the nucleus for tens of
| microseconds, before finally falling to its surface and
| annihilating._
|
| From the research article:
| https://www.nature.com/articles/s41586-022-04440-7
|
| > _The resonance parent states (37, 35) and (39, 35) have
| microsecond-scale lifetimes, whereas the daughter state (38,
| 34) has an Auger width GA [?] 21 MHz (ref. 7; Fig. 1b)_
|
| The life of the antiproton here is too short to make an
| interesting chemistry experiment, but it's long enough to
| measure the spectral lines.
| ethbr0 wrote:
| Dumb question: Why does the antiproton fall to the nucleus'
| surface, after orbiting?
| photochemsyn wrote:
| The stranger case is really the electron, which just sits
| there and never falls to the nucleus (that's the original
| conundrum of the model of the atom as negative electrons
| orbiting a positive nuclear center). Physicists applying QM
| to the hydrogen electron found that the electron could only
| exist in certain energy levels, and drew the analogy of
| standing waves to explain it, hence 'wave equations'. The
| electron is no longer a point orbiting another point, but a
| wave function delocalized over the entire orbital.
|
| These electron quantum rules don't work the same for an
| antiproton, which is 1800X more massive than an electron.
| There's probably some other factors, like the antiproton
| can get close enough to the nucleus for strong force
| effects etc.
| Sharlin wrote:
| An electron orbital overlaps with the nucleus, though;
| any bound electron can in a very real sense be said to
| exist partly inside the nucleus all the time. But
| electron-nucleon physics don't care. In particular the
| electron does not feel the residual strong force. The
| situation is different with a bound antiproton, however.
| If the antiproton wavefunction ends up sufficiently
| overlapping with the wavefunction of one of the nuclear
| protons, they will annihilate.
| fsh wrote:
| It doesn't. The ground state orbital of the antiproton is
| in principle stable, just like the electron orbitals in a
| regular atom. The difference is that antiprotons can
| annihilate with protons from the helium nucleus when they
| get too close. This is why the experiments observe orbitals
| with high quantum numbers where the overlap between the
| antiproton wavefunction and the nucleus is small.
| infogulch wrote:
| I think this is a great question because not too long ago
| we struggled with the opposite question: How can electron-
| based molecules exist at all? (Funny that now I have to
| differentiate it from antiproton-based molecules...) The
| old model of atoms where electrons 'orbited'
| classically/astronomically interpret the electron as
| literally circling around the nucleus, and because a moving
| charge radiates energy electromagnetically it should shed
| it's orbital energy until it reaches the nucleus. This was
| a big conundrum way back before we settled on quantum
| mechanics, which solves this by recognizing that electrons
| 'orbit' is more like an acoustic standing wave and that
| there are a small number/ _quanta_ of available states that
| the electron can possibly exist in. Electron orbitals are
| not continuous or near-continuous, they are very much
| _discrete_ , and there is some minimum activation energy
| required to shift between the various orbital states.
|
| This quora answer actually looks like a reasonable
| description of the issue past physicists faced:
| https://www.quora.com/Why-do-electrons-in-an-atom-keep-a-
| dis...
|
| So I'd guess that the reason why the antiproton's orbit
| decays is because its orbital energy levels are "continuous
| enough" that its orbital energy can decay smoothly down to
| zero. Maybe this is related to the fact that the electron
| is relatively massless compared to the antiproton.
|
| I think it's cool that we found a state of matter where the
| old model of atomic orbital motion that we interpreted as a
| paradox might be a physically accurate description in this
| circumstance.
| puzzledobserver wrote:
| I am not a physicist, but I suppose it is because the
| s-orbital has an amplitude peak at r=0?
|
| In other words, it is not so much the antiproton falling to
| the nuclear surface as much as the antiproton finding
| itself at the nuclear surface.
|
| EDIT: The context is that the antiproton was in an orbital
| with large principal and azimuthal quantum numbers. Still,
| there would be some non-zero probability of the antiproton
| finding itself close to the nucleus, no?
| jbay808 wrote:
| Could we keep it perpetually in an excited state that has
| no amplitude at the centre?
| marcosdumay wrote:
| It reaches the nucleus by a process of tunneling. You can
| never completely stop it, but it reacts exponentially to
| you increasing a barrier.
| jbay808 wrote:
| An excited state isn't a barrier, it's a state with a
| higher energy than ground state. Several non-ground-state
| orbitals have a wavefunction whose amplitude drops to
| zero toward the centre.
|
| An electron won't tunnel to a location where its
| wavefunction amplitude is zero.
| TobTobXX wrote:
| Not too literate in this, but I'd say that the mass of a
| proton is large enough so that quantum effects (such as the
| quantization of of energy) become less relevant than
| classical mechanics (which lets the antiproton get pulled
| toward the proton).
|
| Correct me if I'm wrong though.
| tsimionescu wrote:
| You're wrong. Mass has nothing to do (as much as is known
| at this time) with quantum effects being important or
| not. Quantum mechanics would (as far as we know) work the
| same for a 1kg particle as they do for a 1eV particle.
|
| Instead, the difference is that the antiproton can
| interact with a proton and annihilate, while an electron
| can barely interact with a proton or neutron outside of
| the EM attraction.
| noasaservice wrote:
| My rudimentary guess is either due to the strong and/or
| weak forces combined with lack of orbital/shell velocity.
|
| The antiproton is negative.
|
| The protons with neutrons are collectively positive.
|
| The orbital velocity of the antiproton is slower than that
| of an electron (being something like 180x more massive).
|
| And along with above, the - and + charges attract strongly.
| So the antiproton orbit rapidly decays to the nucleus.
| gus_massa wrote:
| The idea is that electrons, muons and antiprotons have
| stable orbitals, where they can stay forever. For one
| electrons, muons or antiprotons, they have the same shape
| and classification, but they don't have the same size. They
| are all stable.
|
| It's a bad idea to imagine them like a planet orbiting
| around the Sun, or that they suddenly make a turn and
| decide to head to the nuclei, or that they are going in
| spirals until they colide.
|
| In some case, electrons can interact with the nuclei, and
| the nuclei absorbs them, one proton changes into a neutron
| and the process releases a neutrino
| https://en.wikipedia.org/wiki/Electron_capture But the
| electron is in a stable orbital and suddenly it interact
| with the nuclei.
|
| Something similar happens with the antiproton. The
| antiproton is in a stable orbital and suddenly it interact
| with the nuclei and is annihilated.
| BitwiseFool wrote:
| It's been a long time since chemistry and physics class, but
| isn't "orbital" in this context not the same thing as
| gravitational orbits? I was told the concept of orbitals
| represented where an electron could exist around a nucleus
| and that it wasn't actually traveling in a path bound by the
| gravity of the atom. So in this context, how is it actually
| falling into it's surface? Is it just tunneling into contact?
| [deleted]
| gus_massa wrote:
| The important force is the electromagnetic, gravity is very
| weak and you can ignore it in these systems.
|
| For only _one_ electron or one antiproton, the orbitals
| have the same shape and classification. The only difference
| is that the size depends on the mass, so the orbital to put
| the antiproton are much smaller than the orbitals to put
| the electrons. Note that something similar happens with
| muons that have an intermediate mass and the orbital to put
| them have an intermediate size.
| https://en.wikipedia.org/wiki/Bohr_radius
|
| It's more difficult when you have _many_ electrons or muons
| or antiprotons. (I guess nobody had measured a system with
| many muons or antiprotons.) If you have many electrons, the
| problem is that you must calculate the attraction of the
| nuclei and the repulsion of the other electrons, so the
| orbitals change. In particular, the filling rules https://e
| n.wikipedia.org/wiki/Electron_configuration#Atoms:_...
| don't follow the energies of the orbitals of an isolated
| electron.
|
| In a system with many muons or antiprotons, all of them
| will be closer and the repulsion will be bigger, and I
| expect weird filling rules.
|
| Electrons: 1s_up, 1s_down, 2s_up, 2s_down, ...
|
| ???Antiprotons: 1s_up, 2s_up, 1s_down, 2s_down, ... ???
|
| It is possible to calculate the filling order for muons and
| antiprotons numerically, but I'm too lazy do do the
| calculation now and also the standard programs [1] [2] have
| a lot of hidden assumptions to make the calculations with
| electrons more efficient and I'm not sure how difficult is
| to tweak the entry files to calculate this fast enough. [3]
|
| [1] https://en.wikipedia.org/wiki/Gaussian_(software)
|
| [2]
| https://en.wikipedia.org/wiki/PSI_(computational_chemistry)
|
| [3] Perhaps it's implemented and I just need to RTFM, but
| otherwise it looks too straightforward for a PhD thesis,
| but it may be a nice undergraduate thesis.
| hateful wrote:
| Disclaimer: Not a physicist, but have been watching many
| youtube videos. So please correct me if I'm thinking of
| this wrong.
|
| An electron is bound to the nucleus by the electromagnetic
| force, but is not a round ball, but a wave distribution of
| probabilities.
|
| I don't know if it's the actual case, but I've been
| thinking of all "particles" like "waves" in a pool. Small
| disturbances in the fields (e.g. electromagnetic), like
| jumping in a pool. The electron IS the disturbance, because
| to us that is what we can measure (and we can only measure
| one place at a time). So the electron doesn't rotate around
| the nucleus - instead its a wave in the same area where the
| nucleus is. The electron's "probability wave" disturbs the
| space around the nucleus - including inside it, and 1000
| miles away from it. It's just has way more disturbance in
| certain places - AKA "the shell" its in. Just like any
| wave, it "fades" with distance but who's to say where the
| wave ends.
|
| In fact, that wave isn't exactly the same for every
| electron. Each "shell" is waving at a different amplitude
| (is amplitude the right analogy?) - and you can only have
| so many "waves" add up in a shell simply because there's no
| more room because of the length of each wave (like a
| spiral-o-graph). You can only put another wave in the gaps
| of the previous wave (if you did put two in the same place,
| it would double and be part of the next shell, right?). And
| when an electron's amplitude changes, e.g. is lowered, the
| total energy can't be destroyed, so the difference is
| emitted as another wave of the difference - that wave is a
| photon. And the same applies when a photon is added to that
| wave. Like rowing in the water - the exiting wave and the
| rowed wave is added together. I think of Photons are
| partial Electrons. They are like the "wake" of an electrons
| wave change.
| rndphs wrote:
| More or less the right idea. There are actually two
| fields at play here. The electromagnetic field and the
| electron field. The electron field gets quantised into
| electrons and the electromagnetic field quantised to
| photons. The electron field and the electromagnetic field
| are fundamentally separate fields, but they do interact.
| Any particle field with a charge can interact with the
| electromagnetic field. It's the charge that the electron
| field carries that "leaves a wake" in the electromagnetic
| field. In this sense photons are no more partial
| electrons than they are partial protons.
|
| In an atom, the electron state energy comes from the
| electric potential energy due to the electron's charge
| sitting in the electric field produced by the nucleus.
| The further out the charge is, the higher the potential
| energy (and hence the lower the binding energy). This is
| distinct from the electron amplitude. The electron
| amplitude is essentially how much electron is present at
| a point, and lowering it violates conservation laws
| (lepton number, mass, charge).
| pdonis wrote:
| _> how is it actually falling into it 's surface? Is it
| just tunneling into contact?_
|
| Kinda sorta. As fsh responded elsewhere in the thread, the
| difference between the antiproton and an electron is that
| the antiproton can annihilate with one of the protons in
| the helium nucleus (since it's an exact antiparticle of the
| proton, whereas an electron is not). The probability of
| this annihilation happening per unit time depends, roughly
| speaking, on how much the antiproton's wave function
| overlaps with the wave function of the protons in the
| nucleus, which in turn depends on which orbital the
| antiproton is in. But the overlap will be nonzero in _any_
| orbital, which means that this configuration is kind of
| like a radioactive atom: the question is not whether it
| will decay--eventually it will--but how long it will take
| on average. The "half-life" of the antiproton
| configuration in this experiment was on the order of
| microseconds, which is quite long for an antiproton.
| jmyeet wrote:
| So a free neutron will decay into a proton and an electron. This
| already confuses me because the only difference between the
| nucleons is an up quark (uud vs ddd) and an electron an a lepton
| is a fundamental particle.
|
| But an electron in an atom won't merge with a proton to form a
| neutron. There seems to be some hand waving here around the
| strong nuclear force and zero energy state that I don't really
| understand.
|
| But in a neutron star the forces are so great that I believe this
| can happen (or how else does neutronium form?).
|
| And now we see an antiproton can annihilate a proton. Doesn't
| this have the same zero energy problem?
|
| Can someone ELI5?
| ladams wrote:
| Worth noting that a neutron decays into a proton, an electron,
| AND an electron anti-neutrino, so that lepton number is
| conserved (electron is +1 and anti-neutrino is -1). This
| interaction conserves charge and baryon number as well.
| myself248 wrote:
| ITYM ELI27....
| [deleted]
| vikingerik wrote:
| Electrons in an atom do merge with a proton to form a neutron.
| https://en.wikipedia.org/wiki/Electron_capture
| [deleted]
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