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Creating Designer Isotopes
Roland Piquepaille writes "According to a Michigan State University (MSU) news release, 'Made-to-order isotopes hold promise on science's frontier,' nuclear physicists can now start a new career as isotope designers. These scientists can build specific rare isotopes to solve scientific problems and open doors to new technologies. The lead researcher says this approach has already given us the Positron Emission Tomography (PET) scan technology. He's now going further, saying that he wants to build objects 100,000 times smaller than the atomic nucleus. He calls this 'femtotechnology.' Also available are additional details and pictures of the tools used for this kind of research, picked from a 415-page design paper." Update: 05/11 14:30 GMT by SS: Readers have noted that the summary inaccurately portrays the scale of the 'femtotechnology.' The MSU researcher refers to "the capacity to construct objects on an even more minute scale, that of the atomic nucleus 100,000 times smaller."
The term femtotechnology to describe technology built from subatomic particles, as nanotechnology describes technology is not new. The first occurrence of it I've seen was in Pushing Ice. Can anyone provide an earlier reference?
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The size of the atomic nucleus, not 100,000 times smaller. One femtometer is roughly the radius of one atomic nucleus. And unlike the atom as a whole, the nucleus is very compact, about the size of its constituent particles. I don't think any kind of structure 100,000 times smaller than a nucleus has been detected experimentally.
> Atoms of the same element that have the same number of protons
Otherwise they would not be of the same element.
> but different numbers of neutrons (different atomic masses).
I didn't RTFA, but "isotopes are the different versions of an element" translates nicely into "isotopes are the versions of a single element [note the constant number of protons here] with different masses/different numbers of neutrons". You see: element = element, version = same number of protons.
While "different versions" is a somewhat unspecific term, I don't see no misunderstanding of the subject here. If TFA was written for a highly professional audience, I would ask why there was an explanation of isotopes given, anyway, because everybody knows what isotopes are. If not, this somewhat unspecific explanation is more than sufficient and accurate.
I really don't know what your point is.
You cannot build structures with electrons and positrons which are this small. The reason being that the binding energy for EM processes (the strongest force which an e+/- feels) is far too weak to confine the particles to a region as small as 1 fm. For example positronium has a binding energy of 6.8eV, roughly half that of a hydrogen atom and hence it will be slighly larger.
The misconception comes about because the electron is not a particle but a wave. You can trap the wave in a potential but it is still a wave. The smaller the space you want to confine it to the shorter the wavelength required and as the wavelength decreases the energy increases (deBroglie wavelength lambda=Planck's constant/momentum [lambda=h/p]). This means that energies O(10^6) times larger than EM binding energies to confine an electron to such a small area.
The only force we know of that is strong enough to do this is the strong nuclear force which is only felt by quarks. Hence, given our current knowledge, the only thing you could build such a tiny structure out of is quarks...which is why the nucleus is made of these!
This is not an example femtotechnology any more than chemistry is is an example of nanotechnology. All they are doing is sticking protons and neutrons together in ways allowed by nature. This is not "designing" an isotope since there are only a few thousand combinations allowed. That's not to say it isn't useful technology but, if you look at the size of mchines required, the scale of the tech is anything but femto.
Robert A. Heinlein got there first. Tailored isotopes, novella "Blowups Happen". 1930's.
There are a couple of things to keep in mind. First, the more exotic the isotope, the shorter its half life (the average time it takes before undergoing beta-decay and transforming into a slightly more stable element). For most elements there are usually just one to two stable forms. All others will decay, and the further in mass you get from the stable forms, the quicker this decay happens. It's kind of hard to make any physical object with a material that exists for a fraction of a second. Second, for any given element there is a lower mass and an upper mass boundary. There is a physical limit to what types of particles one can create. Beyond these boundaries, called the driplines when applied to the entire nuclear chart, particles are 'unstable'. I use unstable in the vernacular nuclear sense; particles will evaporate from the core until the remaing particles are bound. This, as mentioned above, still doesn't mean the particle is 'stable' in the common sense of the word. Lastly, the NSCL cylcotron produces the rarest particles, the particles with the lowest probability for creation (i.e. very low cross section) at a very low rate, sometimes as low as an event per day. The article is about the construction of a next generation nuclear facility at the NSCL. The US as in all other science fields, is gradually falling behind European and Japanese counterparts. The few other other major nuclear labs in the world (not to be confused with the super-expensive high energy facilities like Cern and Fermilab) are bringing online new facilities that will enable nuclear researchers to study more exotic elements, elements with stranger properties closer to that limit of stability. The MSU proposal is located here: http://www.nscl.msu.edu/future/isf/. There is a lot of interesting research to be done. Many of the biggest unanswered questions in physics are in nuclear physics. One mentioned in the article is the creation of elements. We are indeed created from stars, since the big bang left us with just some helium and hydrogen. The other elements are created in nuclear processes that occur in the giant nuclear furnaces of stars. Interested folks should look online for additional information. There is a incredibly large region of the nuclear chart that currently cannot be reached because present beam facilities don't have the energies and intensities to produce the particles at a rate sufficient for research. It would be very neat if we could get there.