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General Science / Re: Even More Questions that Antimatter to Me
« on: 05/11/2021 02:39:01 »
Hi again.
I'm suspicious you wanted an answer about creating ordinary matter atoms and/or entire molecules. I'm also suspicious you have an eye on the science ficition ideas of creating matter in something like a start trek transporter or whatever the thing is they make stuff in... a replicator I think - where Captain Picard gets his cup of Earl Grey.
Well, making an entire atom all in one go, or straight from a photon is asking a lot but I suppose it's not impossible. The energy of the photon(s) has to match or exceed the total rest mass of the particles you are hoping to create. So for an entire atom of hydrogen plus its partner anti-hydrogen that works out at a photon with an energy of 1.88 GeV or more. I haven't done that calculation... just found it on a web-page but it looks about right. The protons and anti-protons are much more massive than an electron and positron which you could create with just 1.022 MeV. Or to say it another way, the protons need about 1800 times more energy in the gamma ray because they are about 1800 times more massive than an electron. I really don't know if we have equipment to create gamma rays with that frequency, its pretty serious cosmic ray stuff.
Anyway supposing you can get the photons (you know.... on the Google shopping channel it's amazing what you can get these days), you could try and fire those at some dense nuceli and hope for some of them to change into hydrogen plus anti-hydrogen. Now these photons are so energetic that their penetration and absorption characteristics are quite different to the soft gamma rays that produced position-electron pairs. These hard gamma rays will frequently just go through a gold target as if it wasn't there. You'd hope to fire millions of these gamma rays at a gold target and only get a few to interact. There's also very little you can do to stop other particles being created. It's not certain that a proton and an electron would appear, you might just get a proton (and it's anti-proton) and the remaining energy of the photon might just give those protons more kinetic energy than usual. To say that another way, it's not certain that all the energy of the incident photon would be changed into rest mass, some of it might be converted into kinetic energy for a smaller particle. Anyway... the whole process has become extremely random. If you get anything at all it'll be a shower of assorted stuff, some of which would have very high velocities and you'd probably never be able to capture it - but maybe a small portion of that stuff would actually be an entire atom of hydrogen (and anti-hydrogen or bits of anti-hydrogen that have fallen apart).
CERN do not make their anti-hydrogen this way. It's far more efficient to make the smaller components like positrons and anti-protons and then they almost self-assemble themselves into anti-hydrogen. They don't even try to make the anti-protons straight from photons but instead they bombard a metal target with ordinary protons and collect some anti-protons that are produced from that. Even the positrons aren't synthesised from photons, instead these apparently come from a radioactive sodium source that just emits positrons as part of it natural decay process. All they do at CERN is collect these components, slow them down and allow them to come into contact inside a trap and then just wait for self-assembly into anti-atoms. (Information source: https://newscenter.lbl.gov/2010/11/17/antimatter-atoms/).
In principle if you have a pair of anti-hydrogen atoms close together (and cold, i.e. at low velocities) chemistry should take over and they should self-assemble into a complete molecule of anti-Hydrogen gas ( I think the molecular formula has a bar over the H like this ).
Anyway, just focusing on the oridnary matter and not the anti-matter. It would be more efficient to just try and sythesise the protons and electrons (probably in seperate places) and then push those protons through a cloud of electrons. Since they have opposite charges they will attract and self-assemble into atoms of hydrogen at-least a fair portion of the time. We already know that chemisry can take over form here and two atoms of Hydogen in close proximity will self-assemble into a molecule of Hydrogen gas (provided they are cold, i.e. have fairly low velocities).
It's a bit messy and extremely random with high energy gamma rays and high velocity particle fragments flying off all over the place, plus it's a bit of hybrid between sythesising some elementary particles and then just sitting back and waiting for ordinary physics and chemistry to build a molecule for you. However, with a few years of refinement it might look a little bit more like the replicator where Captain Picard gets his cup of Earl Grey tea.
Best Wishes.
1. We can already create pairs of particles using this process, but can we potentially go a little further and create full-on atoms and molecules? Maybe some hydrogen gas or some water or something?You've had a good answer from Halc concerning creation of anti-matter atoms.
I'm suspicious you wanted an answer about creating ordinary matter atoms and/or entire molecules. I'm also suspicious you have an eye on the science ficition ideas of creating matter in something like a start trek transporter or whatever the thing is they make stuff in... a replicator I think - where Captain Picard gets his cup of Earl Grey.
Well, making an entire atom all in one go, or straight from a photon is asking a lot but I suppose it's not impossible. The energy of the photon(s) has to match or exceed the total rest mass of the particles you are hoping to create. So for an entire atom of hydrogen plus its partner anti-hydrogen that works out at a photon with an energy of 1.88 GeV or more. I haven't done that calculation... just found it on a web-page but it looks about right. The protons and anti-protons are much more massive than an electron and positron which you could create with just 1.022 MeV. Or to say it another way, the protons need about 1800 times more energy in the gamma ray because they are about 1800 times more massive than an electron. I really don't know if we have equipment to create gamma rays with that frequency, its pretty serious cosmic ray stuff.
Anyway supposing you can get the photons (you know.... on the Google shopping channel it's amazing what you can get these days), you could try and fire those at some dense nuceli and hope for some of them to change into hydrogen plus anti-hydrogen. Now these photons are so energetic that their penetration and absorption characteristics are quite different to the soft gamma rays that produced position-electron pairs. These hard gamma rays will frequently just go through a gold target as if it wasn't there. You'd hope to fire millions of these gamma rays at a gold target and only get a few to interact. There's also very little you can do to stop other particles being created. It's not certain that a proton and an electron would appear, you might just get a proton (and it's anti-proton) and the remaining energy of the photon might just give those protons more kinetic energy than usual. To say that another way, it's not certain that all the energy of the incident photon would be changed into rest mass, some of it might be converted into kinetic energy for a smaller particle. Anyway... the whole process has become extremely random. If you get anything at all it'll be a shower of assorted stuff, some of which would have very high velocities and you'd probably never be able to capture it - but maybe a small portion of that stuff would actually be an entire atom of hydrogen (and anti-hydrogen or bits of anti-hydrogen that have fallen apart).
CERN do not make their anti-hydrogen this way. It's far more efficient to make the smaller components like positrons and anti-protons and then they almost self-assemble themselves into anti-hydrogen. They don't even try to make the anti-protons straight from photons but instead they bombard a metal target with ordinary protons and collect some anti-protons that are produced from that. Even the positrons aren't synthesised from photons, instead these apparently come from a radioactive sodium source that just emits positrons as part of it natural decay process. All they do at CERN is collect these components, slow them down and allow them to come into contact inside a trap and then just wait for self-assembly into anti-atoms. (Information source: https://newscenter.lbl.gov/2010/11/17/antimatter-atoms/).
In principle if you have a pair of anti-hydrogen atoms close together (and cold, i.e. at low velocities) chemistry should take over and they should self-assemble into a complete molecule of anti-Hydrogen gas ( I think the molecular formula has a bar over the H like this ).
Anyway, just focusing on the oridnary matter and not the anti-matter. It would be more efficient to just try and sythesise the protons and electrons (probably in seperate places) and then push those protons through a cloud of electrons. Since they have opposite charges they will attract and self-assemble into atoms of hydrogen at-least a fair portion of the time. We already know that chemisry can take over form here and two atoms of Hydogen in close proximity will self-assemble into a molecule of Hydrogen gas (provided they are cold, i.e. have fairly low velocities).
It's a bit messy and extremely random with high energy gamma rays and high velocity particle fragments flying off all over the place, plus it's a bit of hybrid between sythesising some elementary particles and then just sitting back and waiting for ordinary physics and chemistry to build a molecule for you. However, with a few years of refinement it might look a little bit more like the replicator where Captain Picard gets his cup of Earl Grey tea.
Best Wishes.
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