Electron microscopes.

[oldman420]

I was Talking to a friend about the latest .06 angstrom electron microscopy results which allow us to see individual atoms.
http://www.npr.org/features/feature.php?wfId=3929860
We wondered if, when we get to the point of being able to see on the subatomic scale will we be able to see individual electrons in their orbits?

I argued that since electrons are a particle that behaves like a wave you might perceive a ring around the atom. My friend stated that he thought that you would be able to capture a ?still? image of individual electrons.

Given that this all theoretical, there is as of yet no answer till they get resolutions down to .006 or smaller angstroms.
This would be interesting to know.
Does anyone have a clue as to which of us is more likely correct?
Thanks AT/HT gurus.



:beer:

 

[Tiamat]

Originally posted by: oldman420
I was Talking to a friend about the latest .06 angstrom electron microscopy results which allow us to see individual atoms.
http://www.npr.org/features/feature.php?wfId=3929860
We wondered if, when we get to the point of being able to see on the subatomic scale will we be able to see individual electrons in their orbits?

I argued that since electrons are a particle that behaves like a wave you might perceive a ring around the atom. My friend stated that he thought that you would be able to capture a ?still? image of individual electrons.

Given that this all theoretical, there is as of yet no answer till they get resolutions down to .006 or smaller angstroms.
This would be interesting to know.
Does anyone have a clue as to which of us is more likely correct?
Thanks AT/HT gurus.



:beer:

I would think that since the electrons are moving close to the speed of light, you wouldnt be able to see them unless you could somehow slow them way way down.

 

[oldman420]

But you are scanning them with electrons that go the same speed.

 

[ZeroNine8]

As far as measurement instruments go, it is very difficult to detect anything smaller than the resolution of your measurement instrument. With advanced statistical analysis of data, you can get a little better than your resolution with some degree of certainty. Using an electron microscope, however, the theoretical limitation of resolution is 1 electron. At this resolution, the electron you are observing will appear as a single 'pixel' in your display. As a general rule, measurement resolution should be 1/10 of the smallest dimension you want to measure, which means you would need to be using something 10x smaller than an electron to get a good representation of one. I realize that electrons don't exactly obey all the laws of classical physics, but the limitations on wave properties and detectable limits would follow similar guidelines. It may be possible to 'see' electrons some day, but I doubt it will be with an electron microscope.

 

[f95toli]

Not exactly, the resolution of an electron microscope depends on the precison of the "optics" (a combination of magnetic and electric fields used to focus the beam) in the column and the acceleration voltage (which is of the order of tens of kV) ; this is because the wavelenght of an electron depends on its speed.

Back to the orignal question, yes I think it is possible to see the orbitals (the symmetry of the "cloud" of electrons surrounding the ions) and as far as I understand this has already been done using SPM-techniques.
However, you can never truly "see" an electron simply because it is a point-particle as far as we know, it does not have a size like a for example a proton (or in other words, it is zero-dimensional).
You also have the problem of the Heisenberg principle; in order to know the exact position of ther electron it need to move with infinite speed, hence in a real experiment all you would see would be a "blured" spot.

 

[ZeroNine8]

there is also the question of what you mean by 'see'. If you merely mean a visual representation of the electron, then you can place a dot on a screen for every electron-volt you detect. Visualizing the presence of an electron is much easier than magnifying the 'image' of an electron.

 

[cquark]

Earlier posters are correct about the electron being a point particle, so there would be no detail to see, but you may be able to see the electron shell shapes of an individual atom. We've examined electrons in particle accelerators at much smaller length scales than you can access with either STM or electron microscopy without discovering any substructure.

You can see some early pictures of atoms using scanning tunnel microscopy (STM) at
http://www.almaden.ibm.com/vis/stm/gallery.html

 

[oldman420]

what if you were able to use a sub atomic particle to scan with?
wouldn't a smaller particle give a higher resolusion?

 

[f95toli]

The electron is a point-particle=has no size, you can not make anything smaller than that.

And, as I have already written, size has nothing to do with it, speed is much more important because that determines the wavelenght of the particle.

 

[silverpig]

Originally posted by: oldman420
what if you were able to use a sub atomic particle to scan with?
wouldn't a smaller particle give a higher resolusion?

Actually, a small yet massive particle would give you the best resolution as the wavelength of the particle gets shorter with increasing mass (the wavelength of me floating through space is something like 10^-50 m or something IIRC).

So basically, the best you can do is an electron (small... point mass) and make it go really really fast.

 

[Cogman]

I dont think you could see an electron with and electron Microscope, The electrons that you are shooting in would be defracted by other electrons and the picture would be scewed. Now, if we could create a Neutrino Microscope, then It might be a diffrent story.

 

[cquark]

Originally posted by: Cogman
I dont think you could see an electron with and electron Microscope, The electrons that you are shooting in would be defracted by other electrons and the picture would be scewed. Now, if we could create a Neutrino Microscope, then It might be a diffrent story.

Neutinos are less massive than the electron, but there's no indication that they're any smaller.

The real problem with a neutrino microscope is that the weak nuclear force is, as its name implies, weak. Billions of neutrinos have gone through your body without interacting with any of its particle as you read this sentence. We have to build detectors like SNO that consist of a thousand tons of heavy water and around 10,000 photomultiplier tubes buried over a mile deep to shield it from interference just to see a few neutrinos every year.

 

[DrPizza]

More detailed article

Microscope focuses on sub-Angstrom scales
16 September 2004

Scientists have imaged a crystal on sub-Angstrom scales by exploiting a new technique to correct the aberrations in a scanning transmission electron microscope. Although microscopists realized 50 years ago that it would be possible to make these corrections, the technology needed to do this has only just been developed by researchers at the Oak Ridge National Laboratory in Tennessee and Nion, a company based in Washington state (P D Nellist et al. 2004 Science 305 1741).

Sub-Angstrom imaging has been a long-standing goal for electron microscopists because it would allow structures to be studied at the level of single atoms. Although sub-Angstrom information can be obtained by post-processing electron micrographs, it has not been possible until now to obtain this information directly.


Crystal clear
A scanning transmission electron microscope builds up an image by scanning an electron beam across a sample and measuring the parts of the beam that are transmitted back from the sample. However, the aberration -- or blurring -- that is caused by the magnetic lenses that are used to focus the electron beams has limited the resolution of these instruments to around 1.5 Angstroms (1.5x10-10 metres), which is slightly larger than the typical distance between atoms.

The resolution of an electron microscope increases as its aperture becomes larger but in the past lens aberrations have caused the images to blur once the aperture has reached a certain size. To overcome this problem, Stephen Pennycook of Oak Ridge and colleagues fitted an aberration corrector, made by Nion, onto their scanning transmission electron microscope. This corrector is a lens that employs software that is capable of analysing all axial aberrations in the microscope in less than a minute, and then making automatic adjustments to compensate.

The Oak Ridge-Nion team tested its device by imaging a silicon crystal in which the columns of atoms are known to be 0.78 Angstroms apart. Before correction, the optimum resolution for images was 1.3 Angstroms, but after correction it was possible to resolve the individual columns of atoms (see figure). The technique allowed the team to effectively double the aperture size of the lens.

"You can think of aberration correction as a pair of spectacles for a microscope," says Pennycook. "Previously the vision was blurred but now we can see twice as clearly as before."

"Seeing atoms more clearly allows us to see materials better, to understand how atoms go together so we can understand how things behave the way they do," he adds. "The advance benefits a vast array of fields, from chemical sciences, material science and nanotechnology -- everywhere people want to see what they have made."

The team now plans to explore the possibility of using its device to image in 3D.

About the author
Belle Dumé is Science Writer at PhysicsWeb

(came from here

 

[iwantanewcomputer]

theoretically if there was just one electron in the field of view and you shoot a buch of electrons at it and one hits it and bounces back you could detect that 1 electron. however the probability of hitting the electron and the probability of it hitting one of the detectors and creating a noticable voltage signal is next to nothing

 

[f95toli]

No, because it is the WAVELENGTH of the electron that matters. You can NOT model this as a bunch of particles hitting each others, at these length-scales you need quantum mechanics to understand what is going on.

That said it is true that the charge of the electron is a problem if you want to image other charged particles, I know there has been some succesfull attempts to make neutron microscopes with relatively low resolution.
A working neutron microscope would in principle be very sensistive. The problem is you need to accelerate the neutrons somehow and you also need a way to make efficient optics, this is a really tricky problem

 

[FrustratedUser]

No, you can not see electrons with a Sweep Electron Microscope.