EPTFirst-Ever Images of an Electron In Orbit - Page 4
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Taekwon
United States8155 Posts
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Jameser
Sweden951 Posts
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GeedrAhsc
United States97 Posts
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XiGua
Sweden3085 Posts
XD Anyways, looks very interesting! | ||
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Orpheos
United States1663 Posts
also it is important to note that this only worked in a certain case of molecule, namely one that has a high aspect ratio laterally. think of it like a sheet of paper | ||
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Ygz
England370 Posts
Awesome news anyway! | ||
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Fleshcut
Germany592 Posts
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Diizzy
United States828 Posts
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Nycaloth
147 Posts
There are some misconceptions and presented so far and id like to rectify that a bit and give a very general explanation on what we see and what it means. The pictures we see are taken by very advanced microcopes, the techniques used are scanning tunneling mocroscopy (STM) and atomic force microscopy (AFM). though called that, they are not microscopes in the "traditional" sense and do not use light and lenses to peek into the very small. instead, both work by scanning a surface with a very narrow metal tip and recording certain surface properties at different points. these measurements can be combined into pictures of the surface, single measurements being the pixels combining the picture. Through the use of piezo crystals and sofisticated dampening of the tip-sample system as a whole, the motion of the tip can be controlled very precisely, on scales smaller the the diameter of an atom. understanding of both techniques requires a basic familiarity with quantum mechanics, but the wikipedia articles on the subject should be enough to explain how exactly they work. Since we are doing quantum mechanics (QM), one has to be exceedingly careful when using terms such as "position", "velocity" or "path", since they cannot usually be defined in a meaningful way any more. i cant read the full article referenced in the OP at the moment since im not at the university and dont have access to it, but what we see in the pictures are molecular orbitals. what QM can only predict possibilities and other statistical quantities. orbitals are such a quantity, they represent the possibility to find an electron within a certain volume of space. this quantity can be computed numerically for complex systems such as molecules and these days can be measured by STM. due to electronic properties, namely the pauli exclusion principle, only two electrons can fit into one of these orbitals at a time. they are filled up until all the electrons in the molecule are used up. Thus, wer get the highest occupied molecular orbital, the HOMO, and the lowest unoccupied moelcular orbital, or LUMO. these two are usually involved when the molecule exchanges charge with its surroundings, eg during the formation of chemical bonds, which makes them interesting for study. what can we learn from this? well, by studying the electronic properties of molecules, we can learn something about their behaviour! and since the STM and AFM also allow us to manipulate single atoms and molecules, we can start building things on this scale. our hope is that by understanding molecular interaction on this small scale, we will be able to build circuitry, memory or other useful things from molecular building blocks. a few advances have already been made in this area, as researchers have found molecules that can act as switches or rectifiers or have other potentially useful properties. ill be happy to try and answer any questions on the topic! | ||
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Vei
United States2845 Posts
they do follow an orbit, it's just that to OBSERVE it we have to interfere with its orbit so we can never really know. | ||
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Nycaloth
147 Posts
On August 30 2011 05:58 XiGua wrote: Lol, my asian scientist dad is saying: "Everybody knows this. These kinds of pictures have been taken before." XD Anyways, looks very interesting! true, but for some reason, few people outside the scientific community have taken notice of this. which is a bit of a shame, seeing how it is a very exciting area of research. | ||
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SocialisT
Sweden160 Posts
Now chemistry teachers over the world can actually say that this IS the way it works, and not just come with theories :D | ||
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jgoonld
334 Posts
On August 30 2011 06:49 Nycaloth wrote: The pictures we see are taken by very advanced microcopes, the techniques used are scanning tunneling mocroscopy (STM) and atomic force microscopy (AFM). though called that, they are not microscopes in the "traditional" sense and do not use light and lenses to peek into the very small. instead, both work by scanning a surface with a very narrow metal tip and recording certain surface properties at different points. these measurements can be combined into pictures of the surface, single measurements being the pixels combining the picture. Through the use of piezo crystals and sofisticated dampening of the tip-sample system as a whole, the motion of the tip can be controlled very precisely, on scales smaller the the diameter of an atom. understanding of both techniques requires a basic familiarity with quantum mechanics, but the wikipedia articles on the subject should be enough to explain how exactly they work. Since we are doing quantum mechanics (QM), one has to be exceedingly careful when using terms such as "position", "velocity" or "path", since they cannot usually be defined in a meaningful way any more. i cant read the full article referenced in the OP at the moment since im not at the university and dont have access to it, but what we see in the pictures are molecular orbitals. what QM can only predict possibilities and other statistical quantities. orbitals are such a quantity, they represent the possibility to find an electron within a certain volume of space. this quantity can be computed numerically for complex systems such as molecules and these days can be measured by STM. due to electronic properties, namely the pauli exclusion principle, only two electrons can fit into one of these orbitals at a time. they are filled up until all the electrons in the molecule are used up. Thus, wer get the highest occupied molecular orbital, the HOMO, and the lowest unoccupied moelcular orbital, or LUMO. these two are usually involved when the molecule exchanges charge with its surroundings, eg during the formation of chemical bonds, which makes them interesting for study. Thanks for the insight! I don't have much knowledge of this field, but I have some questions about what they're looking at. How are pure "photos" of the HOMO and LUMO (or at least electron probability densities of electrons at these certain energies) obtained? I assume that they excite electrons into the HOMO to get the images of it, but won't there continue to be electrons in lower energy MO's? And wouldn't the same be true for LUMOs? How are they isolating electrons in certain orbitals for viewing while not sensing all of the other electrons in the molecule? | ||
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Badfatpanda
United States9719 Posts
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Toadesstern
Germany16350 Posts
On August 30 2011 07:06 The_PhaCe wrote: This is absolutely stunning news. Wow. Now chemistry teachers over the world can actually say that this IS the way it works, and not just come with theories :D well, the first thing my prof said was something along the lines "the funny part of physics is that you can't really proof anything. If your experiment shows that it's wrong, than your theory is most likely wrong. However if your experiment got the results you're expecting the only thing you can say is, that maybe (!) you're not wrong but you won't be able to say that you're right" sooo kinda :p But yeah really stunning. | ||
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Simberto
Germany11491 Posts
On August 30 2011 06:51 Vei wrote: they do follow an orbit, it's just that to OBSERVE it we have to interfere with its orbit so we can never really know. Nah. At least not the same sort of orbit a planet has around the sun. Because a circular motion means constant acceleration, and when you accelerate an electron, it emit radiation, meaning it would lose energy at a very rapid rate. I don't remember the exact numbers, but atoms would only last a ridiculously small amount of time if electrons actually moved around an orbit. At least this is the main reason that people started to think about other models than the rutherford-atom model, which basically is electrons moving like planets. | ||
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Ympulse
United States287 Posts
They knew about atoms in 1911? Source please. | ||
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synapse
China13814 Posts
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CowMoo
United States45 Posts
We can never know where electrons exactly are without disturbing their velocity/path whatever. Heisenberg uncertainty principle bla bla bla. Instead we have this "probability function" idea. Think of a flat plane in the x-y axes, and then for every x and y, give it a specific height. So what you have now resembles a flat landscape with mountains and hills poking up. The height at any point represents the probability that an electron will be there if you randomly check for it. + Show Spoiler + If you're good with mental pictures, you can try and visualize this in 3D with color (for every point x,y,z, associate a color that represents probability, e.g. red = high probability and blue = low probability). Now think of the AFM as a needle, suspended from the sky, that sweeps through this landscape at a specific height, pretty low. If you hit something, you know that an electron has a pretty good chance of hanging out there fairly regularly. You can trace the borders of these hills and make a "topographical map" of sorts of the probability function. They took data on this atom with the AFM, filled in the places where they hit something with white, and left everything else dark. What you have left is the white part represents a high probability of finding an electron there, and the black parts mean that it would be exceedingly rare to find an electron there. What's cool is this happens to match the probability fields that people have been predicting for quite a while. I apologize for some of the gross oversimplifications that physicists will feel I have made, but this interpretation has served me pretty well as an engineer. | ||
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kunstderfugue
Mexico375 Posts
On August 30 2011 11:37 Ympulse wrote: They knew about atoms in 1911? Source please. http://en.wikipedia.org/wiki/John_Dalton They knew about atoms in 1911. http://en.wikipedia.org/wiki/Ernest_Rutherford He thought electrons moved in orbits around atoms *about* one hundred years ago. | ||
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