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Most Detailed Photos of an Atom Yet
BuzzSkyline writes "Ukrainian researchers have managed to take pictures of atoms that reveal structure of the electron clouds surrounding carbon nuclei in unprecedented detail. Although the images offer no surprises (they look much like the sketches of electron orbitals included in high school science texts), this is the first time that anyone has directly imaged atoms at this level, rather than inferring the structure of the orbitals from indirect measurements such as electron or X-ray interferometry."
This is amazing. We'd theorised orbitals to exist, and they worked very well. We could calculate the shapes of molecules and make detailed predictions that came true to 10 decimal places. Quantum mechanics as applied to electrons in atoms is the most successful and the most rigorously tested theory ever developed.
And yet, to finally see a real orbital, not a simulation. Looks like a 1s and a 2p, right there for the looking!
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The unscaled photo is here:
http://insidescience.org/polopoly_fs/1.918!image/671260397.jpg
The shadows are all wrong.
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Physicists are not photographers! They obviously had the shutter speed too low - Look how blurry the picture is!
It pays to be obvious, especially if you have a reputation for being subtle.
Why? Because the "orbitals" are actually solutions of the Schroedinger Wave Equation. They are images or a probability distribution in abstract space. Electrons are not clouds or points, they are things we don't really understand but describe by means of quantum mechanics. So I am deeply suspicious of the picture, because there is no physical object of that shape to image.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
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(not actual size)
So this is what's powering my netbook!
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can't really call it a photograph if it was taken with electrons rather than light.
I wonder how they can tell the electron is blue?
being vague is almost as cool as doing that other thing...
They do look like the classical orbitals, don't they?
However, there are some problems with interpreting the image as a photograph of an orbital. What the FEEM does is to charge up a very sharp point. The actual voltage may not be very big, but the local field strength depends on screening and curvature, so you can get very large electrostatic fields around sharp features, and if you get the balance right, electrons will leave the sharp points, zoom down the field lines, and get imaged. I remember seeing a sharp tungsten needle in a FEEM back in the seventies, and seeing the individual atoms. This sort of thing provided the first real evidence of a screw dislocation. You got a strange projection of the tip of the needle, as the electrostatic field tended to map the roughly spherical tip onto a flat plane.
So what is happening here? Our field stripping an electron from the orbital. We are getting a map of the electron flows as focused by the electrostatic field. We calculate the trajectory back through the electrostatic field and guess some sort of map of emission. They must have stripped hundreds or thousands of orbital electrons from the same atom, and replaced them to get each image. However, if an orbital 'pokes out' of the atom, or forms a 'sharp feature' (inverted commas because they are wave functions, so these concepts are a bit hard to define) then we get a bright spot. The really cool bit is getting the atom to go back to the same hybridization state hundreds of times, so we got the two-lobed picture.
It's dead clever. However, for my money, the atomic force probes are cooler as they can measure the fields without stripping the electrons. But, as the reviewer said, it takes all sorts...
Looks like a smurf sat on the photocopier.
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Thanks for responding. This could do with some mod points but I can't mod and post...so I'll respond. It's interesting to think about what is happening here. It's possibly unhelpful to refer in the same sentence to "current" and "electrons" but I know what you mean, though I would rephrase it a little to help my own understanding. The "current" did not cause the carbon atom to give off electrons; rather, the potential difference enabled some electrons to pass along the carbon chain until they left the tip, and the path of the emerging electrons was probabilitistically interfered with in a way that reflected the solution of the Schroedinger wave equation for the outer electrons of the end atom. That's a very interesting experiment. The benefit of using carbon atoms in a molecule is that the bond angle presumably locks the orientation of the P orbitals sufficiently to enable the experiment. So for many atoms it simply wouldn't work, and what we are seeing here is not an image per se but something more like the result of the Rutherford/Geiger/Marsden experiment. It looks like a significant experiment, but the summary is quite wrong as to what is being shown.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."