By Josh

2012-11-12 08:42:17 8 Comments

I was thinking one day and came up with a theory after reading about how scientists were studying anti-matter by using electro magnetic fields to separate matter from the anti-matter they made. It got me thinking would it be possible to use very powerful electromagnetic fields to break down the atomic structure of objects or build things in this way?

Is this atomic reconstruction with electromagnetic fields theoretically possible? That is, is it theoretically possible to use electromagnetic fields generated by a machine to separate the parts of an atom thereby deconstructing an object on the atomic/subatomic level?

I'm not asking about breaking molecular bonds but rather actual atoms apart. If it's possible to break atoms apart with electromagnetic fields, is it also possible to use a similar process to assemble them?


@Patrick Jean-Marc Louise 2019-10-19 23:09:11

Electric strength =5.145175226 X 10^11N/C Magnetic strength = 235125.6635 T so Velocity of the electron = E/B =2.188266.117 m.s^-1 = C/137

@Emilio Pisanty 2013-01-01 21:08:25

It is doable, easily, if you consider time-dependent EM fields - or, more specifically, pulses of light. This is because light can be focused into a tight focal spot of ~ wavelength size, thus squeezing a lot of energy (and thus EM field) into a tight spot. This is impossible using static fields, which can't reach maxima except at their sources. Just as importantly, one can prepare really short pulses of radiation that compress into a short (i.e. few femtoseconds) time the energy stored in a laser medium over a millisecond or so. This allows quite modest energies - of millijoule order - to create electric fields comparable with the atomic electric fields (as in John Rennie's answer) for long enough to ionize just about any atom.

Note that this does not need a macroscopic sample (although actually observing stuff usually does!). If you manage by some means to get a single atom to sit still at a known position (which is a doable but nontrivial exercise) then firing enough strong laser pulses will ionize it, releasing one electron. You can of course release more electrons but it will naturally get harder and harder (so that triple ionization is the most you can hope for). Photon energies (which are proportional to the frequency) are not really a concern in this high-intensity regime, where multiphoton ionization and tunnel ionization take over as the main mechanisms as one goes from optical to IR and lower frequencies.

Regarding the converse in your question, we have nothing like the technology to "atomically print" a table, atom by atom, and I would question the feasibility of such a scheme. Optical tweezers, for example, can be used to move molecules around and depositing them on a surface could potentially work, but their spatial resolution is limited (by the wavelength, which can't be too short or stuff starts to break). Even worse, you'd have to work at it for something like geological-scale times to get anything sizable.

On the other hand, metamaterials are a good example where we can build materials to atomic-scale detail so that they have the macroscopic properties we want, including such exotica as negative refraction indices or strongly chiral media. While it does not exactly fit the bill you ask for, I think it is fundamentally more cool with the added bonus of being feasible.

@John Rennie 2012-11-12 09:40:33

It's exceedingly difficult to tear apart an isolated atom with an electric field. It's a lot easier to ionise a gas of many atoms, but the mechanism is different. Let's stick to an isolated atom for now to see why it's hard.

Consider an isolated hydrogen atom. The binding energy of the proton and electron is 13.6eV and the average separation is about 0.05nm. So to tear the electron and proton apart you need a field gradient of about 13.6V per 0.05nm. Converting this to more sensible units gives about 2.7 $\times$ 10$^{11}$ volts/metre, and this is far above what we can create in the lab.

I did say it's easier to ionise a gas of many atoms. Suppose you apply a strong electric field to a hydrogen gas, and suppose there is a stray electron somewhere in the gas. Let's not worry where the electron came from; maybe a passing cosmic ray produced it. Anyhow, the free electron will start to accelerate along the electric field lines and at some point it will crash into an atom. If the collision energy is significantly greater than 13.6eV the electron will ionise the atom it hits, and now you have two free electrons. Those two electrons will in turn accelerate and collide with other atoms and you get an electron avalanche. The mean free path of an electron in air is about 0.5 microns, so the corresponding electric field is 27MV/m and this is easily achievable. There's more on this in the Wikipedia article on Paschen's law.

@anna v 2012-11-12 09:52:29

"How does it work? : An Ecoflow ionises the fuel by directing a specific and powerful static magnetic field right into the fuel supply line. Through a process known as magnetohydrodynamics the fuels ability to combine with oxygen improves and greater energy Is released from the fuel."… . One can ionize with magnetic fields. There is also the triboelectric effect.ionisation by rubbing which shows that the energies are easily available.

@John Rennie 2012-11-12 10:01:46

@annav: my interpretation of the question is whether it's possible to tear apart an isolated atom with just an electric field, and the answer is "in practice, no". Triboelectricity doesn't seem to me to have any connection with what the OP is asking.

@spherical chicken 2012-12-02 17:16:26

@John Rennie Hi John, the scale of the electric field strength for ionizing one single hydrogen atom is not that impossible, according to my materials. If we take the electric-field of a laser into account, then the $2.7\times10^{11}$V/m(or $2.7\times10^{9}$V/cm) corresponds to an intensity of approximately $1.9\times10^{16}$W/cm^2. A paper from Optical Society of America named 'Relativistic Optics' said a record intensity of $10^{21}$ W/cm^2 has been demonstrated in University of Michigan, and that was in 2004.

@John Rennie 2012-12-03 07:04:15

@sphericalchicken - A laser produces an intense electric field over a very short distance. An optical laser will not ionise an isolated hydrogen atom because its photons contain too little energy. In a gas of hydrogen atoms it may cause ionisation due to heating, and the resulting atomic collisions, but this isn't what the question was asking.

@Michael 2019-08-16 22:28:04

Why do you need 2.7E11 V/m if you aren't a meter away? In other words, can't you do it with a lower energy field if you are closer to the atom?

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