Is there photographic proof of the atom's existence?

[haribol]

Are there any photographic proof of the atoms, electrons, protons and all these particles? Or do we simply see the effects of these so called particles and conclude from that evidence that there must be some sort of particles?

 

[selfAdjoint]

The scanning tunnel microscope (STM) has produced actual photographs of atoms. I don't know if electrons have been photographed - if they have it's probably a shot of an atomic electron shell. Note that any photograph takes time to register the image on the plate, so what you see would be an "integrated" version in which uncertainties would tend to wash out.

OTOH, the famous double slit images could be considered electron photographs of a kind.

 

[Janitor]

I saw a 'picture' (to use a more neutral word than 'photograph') of atoms of some kind that had been manipulated by an STM to lie on a substrate in a pattern that spelled out "IBM" if I remember correctly. I also saw a picture of something called a "quantum corral" done in the same way.

 

[ZapperZ]

Are there any photographic proof of the atoms, electrons, protons and all these particles? Or do we simply see the effects of these so called particles and conclude from that evidence that there must be some sort of particles?

The problem with answering a question like this is that (and other questions that involves "have we seen it?"), if one really thinks about it, the question is rather vague. What does it mean as "photographic PROOF"? Is it the same way that you and I take photographic pictures when we go on a vacation? This then involves the collection of reflected light (light reflecting off the subjects) into either a light sensitive photographic film, or in the digital age, a CCD camera, which in turn, causes various chemical and/or physical reaction and tries to store that information based on a calibration of what color and intensity it should display. We then "see" this info based on our viewing with our eyes, that in turn processes that info to our brains, and thus, we "see" it.

One needs to be aware that EVERYTHING that we know and accept to "exist" (at least in science) is based on the fact that each one of them has a set of properties and characteristics. We DEFINE them based on those characteristics. The same way with an atom. We have a set of definitions of what an atom is, and when we test or make a measurement, if that thing we're testing has the same characteristics of what an atom is supposed to have, then that is an atom. The atom was NEVER defined based on what we can SEE. It was defined based on a set of characteristics (energy states, orbital angular momentum, etc.) that require measurements of those characteristics to verify its existence".

The STM images that have been mentioned in this string illustrate just that very point. STM images record either a variation in voltage or tunneling current between the position of the surface and the STM tip. The positional scan resolution can be as high as the size of an atom. This then is displayed as a false-color scale. Again, what is being done is the measurement of various properties of the surface, which is then recorded and displayed in an "attractive" fashion for human consumption. Is this measurement the same as the run-of-the-mill "photographic proof"? No, but it is essentially the identical exercise as a photographic proof.

Zz.

 

[Njorl]

Really, you can only have photographic proof of photons.

Njorl

 

[Nenad]

when it comes down to the quantum world, we still do not know what anything looks like. Because our perception of photography is photons entering a lens. In the quantum world, there is uncertanty, which means you can't really look at these particles. At least that's what I think.

 

[shrumeo]

Also, in HRTEM images, you can see the columns of atoms in a lattice.
Now that the new generation of spherical-aberration-corrected TEMs are coming out you can get images that look like "ball and stick" models of your lattice.

A group down the hall from us uses Aberration-Corrected Z-STEM on CdSe quantum dots.
Here is a link to their latest paper in Nano Letters (ASAP) if you have access:
http://pubs.acs.org/cgi-bin/asap.cgi/nalefd/asap/html/nl049406q.html

I attached an image in case you don't. See attachements.

 

[shrumeo]

Really, you can only have photographic proof of photons.

Njorl

Not quite, it's really whatever will "expose" a certain medium. In our old clunker of a TEM, we still use film plates, which are exposed by electrons. So you have photographic proof of electrons I guess.

Then, I think there were plates that are exposed when alpha rays and are used (OLD school), so that would be photgraphic proof of alpha particles.

When i go downstairs to use the van der Graaf accelerator, we use thermal paper to tell where the proton beam is striking before we put our target in the same place. A photographic proof of protons.

 

[FZ+]

I don't know if electrons have been photographed - if they have it's probably a shot of an atomic electron shell.

Does this one count?

Big bumps are iron atoms, and the ripples are electron standing waves.

 

[Janitor]

I love that quantum corral pic, FZ+.

 

[robphy]

More (including the "IBM" one)
http://www.almaden.ibm.com/vis/stm/library.html
http://www.physics.purdue.edu/nanophys/stm.html

 

[Janitor]

Art meets nanotechnology!

 

[pelastration]

http://www.nsf.gov/home/hghlghts/990914.htm

Images -- not computer simulations -- of dumbbell-shaped clouds of electrons shared between copper and oxygen atoms in cuprite (C2O) in a formation known in quantum mechanics as the s-dz2 orbital hybridization.
This image, obtained by ASU solid state scientists Jian-Min Zuo, Miyoung Kim, Michael O'Keefe and John Spence using electron and x-ray diffraction techniques, represents the first time the covalent bonds between atoms have ever been "seen" in cuprite. The nuclei of the copper atoms (not shown) are at the center of the blue and red shaded orbitals and those of the oxygen atoms (also not visible) are at the center and corners of the superimposed cube. The fuzzy pink clouds are less defined electron clouds representing covalent bonds between the copper atoms -- metal to metal bonding. In the second image (Cu202.tif), superimposed red circles represent the locations of oxygen nuclei.

The technic: CBED is a microanalytical technique that uses a convergent or focused beam of electrons to obtain diffraction patterns from small specimen regions. CBED patterns consist of discs of intensity (rather than spots) which are rich in detail and can be exploited to reveal various aspects of specimen microstructure1,2. Spatial resolution is determined by the focussed incident probe size.


My remark: The copper atom shown on these photos have a fine "top". A very strange zone indicating some extra electron distribution. Why?

 

[Janitor]

I don't know if this has been done--and if it has not been done, probably there are technical reasons that make it too hard--but it would be neat to see a STM image of a small protein lying on a substrate, or a snippet of nucleic acid with a dozen or so base pairs. Would the double helix geometry of a small piece of DNA be visible in that way? Or would the interaction with the substrate atoms warp the DNA piece so badly that it would lose its helical shape?

 

[pallidin]

Excellent images!
Looking through robphy's second link, I discovered this gem with regards to TEM images of the STM tips used. Fascinating!
http://www.physics.purdue.edu/nanophys/uhvstm/tip.html

 

[Janitor]

The STM tips look downright low-tech, don't they?

 

[shrumeo]

I don't know if this has been done--and if it has not been done, probably there are technical reasons that make it too hard--but it would be neat to see a STM image of a small protein lying on a substrate, or a snippet of nucleic acid with a dozen or so base pairs. Would the double helix geometry of a small piece of DNA be visible in that way? Or would the interaction with the substrate atoms warp the DNA piece so badly that it would lose its helical shape?

Here is just one paper (abstract) there are many more, surely.

Extended Structure of DNA Oligomer and Nucleotide Imaging Studied by Scanning Tunneling Microscopy
Chiho Hamai, Hiroyuki Tanaka, and Tomoji Kawai
The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan

Abstract:
DNA oligomers deposited on Cu(111) surfaces were observed at liquid nitrogen temperature using a scanning tunneling microscope. The observed oligomers were pAAAAAAATTTTTTT (14mer), pTTTGGTTAACCAAA (14mer), pGGGGGTTTTTTTTTT (15mer), and pAAAAAAAAAATTTTTTTTTT (20mer). The structure of the isolated oligomers adsorbed on the Cu surface varies with the length of the molecular chain. The isolated 20mer is adsorbed to aggregate three-dimensionally. The isolated 14mer and 15mer are extended on the surface, and the almost entire molecular chain touches the surface. A highly resolved image of the 20mer shows bright spots aligned in a row along a single-stranded DNA with the same periodicity as that of the nucleotide units, demonstrating that each bright spot is a nucleotide.

 

[shrumeo]

http://www.nsf.gov/home/hghlghts/990914.htm

Images -- not computer simulations -- of dumbbell-shaped clouds of electrons shared between copper and oxygen atoms in cuprite (C2O) in a formation known in quantum mechanics as the s-dz2 orbital hybridization.
This image, obtained by ASU solid state scientists Jian-Min Zuo, Miyoung Kim, Michael O'Keefe and John Spence using electron and x-ray diffraction techniques, represents the first time the covalent bonds between atoms have ever been "seen" in cuprite. The nuclei of the copper atoms (not shown) are at the center of the blue and red shaded orbitals and those of the oxygen atoms (also not visible) are at the center and corners of the superimposed cube. The fuzzy pink clouds are less defined electron clouds representing covalent bonds between the copper atoms -- metal to metal bonding. In the second image (Cu202.tif), superimposed red circles represent the locations of oxygen nuclei.

The technic: CBED is a microanalytical technique that uses a convergent or focused beam of electrons to obtain diffraction patterns from small specimen regions. CBED patterns consist of discs of intensity (rather than spots) which are rich in detail and can be exploited to reveal various aspects of specimen microstructure1,2. Spatial resolution is determined by the focussed incident probe size.


My remark: The copper atom shown on these photos have a fine "top". A very strange zone indicating some extra electron distribution. Why?

This is strange to me because, normally, single crystal Xray diffraction (and electron diffraction) patterns allow you to contruct electron density maps that are thermally averaged over the whole crystal, or at least where the beam is shining.

I don't understand how they were able to take a CBED pattern and calculate the shapes of hybridized orbitals.

I couldn't find any images but, copper(II) is d9 and notorius for Jahn-Teller distortions. This is might be the extra e-distribution you were talking about?

 

[ZapperZ]

One also needs to be careful (I seem to be saying that a lot lately) in thinking that one gets the real space distribution from x-ray and electron diffraction. What one gets directly from these experiments is the reciprocal space intensities which allows one to obtain, for example, the Brillouin zones. Only from this can one go on to construct the real space intensities, either by direct conversion (if it is a "simple" lattice) or via a Fourier transform.

So I'm not sure if one would consider these diffraction technique as a direct "photographic" picture of an atom, a lattice, or an electron cloud.

Zz.

 

[shrumeo]

exactly

how in sam hill did they get a picture that looked like bulbous orbitals?
I can understand how they got lattice info, but orbital info? I didn't think CBED was that powerful.

Oh, wait, this explains it all:
http://www.ias.ac.in/currsci/nov10/RESEARCHNEWS.PDF

edit: hehe, the article says that the team recently developed CBED :)
I'd like to tell that to my Electron Diffraction book!

All they did was determine if there was covalency between the copper atoms, no photography.

 

[ZapperZ]

exactly

how in sam hill did they get a picture that looked like bulbous orbitals?
I can understand how they got lattice info, but orbital info? I didn't think CBED was that powerful.

Oh, wait, this explains it all:
http://www.ias.ac.in/currsci/nov10/RESEARCHNEWS.PDF

edit: hehe, the article says that the team recently developed CBED :)
I'd like to tell that to my Electron Diffraction book!

Well, pay attention to the part where it says ".. a theoretical electron density map was generated..."

So using the highly specialized CBED data and the structure factor from x-ray diffraction, they "constructed" the electron density map in real space. There's nothing wrong here, but it would be misleading to say that this is a direct visual observation. STM images are more "direct" than this.

Zz.

 

[shrumeo]

yes, as I said earlier, all diffraction data gives you is an electron density map (except for neutron diff. which tell you where the nuclei are)

this thread was about photographing atoms

 

[Janitor]

Thanks for the information on DNA having been looked at by an STM, shrumeo. It sounds like around 14 or 15 bases, the DNA is badly warped, as my intuition suggested it might be. But at 20 bases, it was observed "to aggregate three-dimensionally," according to your quote. Can you shed some light on what that means? Are they saying that while it may not have looked helical, at least it wasn't pancacked flat against the copper?

 

[shrumeo]

I'm just now realizing that the citation isn't with the abstract. It's:

J. Phys. Chem. B. 104(42), 9894-9897

I'm not sure if I can find info in the paper that will answer your question, but here are a few quotes.
-----------
"Figure 2 reveals that the adsorbed structure of the 20mer is different from those of the 14mer and 15mer. The molecular chains in the 14mer and 15mer images can be traced from end to end, indicating that 14 mer and 15mer are adsorbed so that their almost entire chains touch the surface. Conversely, the 20mer chain images cannot be traced from end to end: it has a large number of three-dimensionally overlapping parts. This indicates that the stable adsorbed structure varies with the chain length. It is expected that the adsorbed structures depend on the adsorption process. The 14mer and 15mer entangled in solution would be flattened on the surface by the forces given to the oligomer during adsorption. The forces at the adsorption, however, are too weak to completely unfasten and flatten the entangled 20mer."
------------

So I guess you are right that it wasn't flattened onto the surface, but the 14 and 15 mers were.

 

[pelastration]

I couldn't find any images but, copper(II) is d9 and notorius for Jahn-Teller distortions. This is might be the extra e-distribution you were talking about?

Thanks Shrumeo. I will try to find out more about your suggestion.

 

[shrumeo]

uh oh :)

I wouldn't put TOO much value into what I say. I don't even know if its Cu(II) in their crystals.

All I know is that, at least in molecular complexes, metals with a d9 configuration usually exhibit Jahn-Teller distortions. This will either elongate metal-ligand bonds that lie along the z-axis, or expel the ligand completely (actually, never letting it bond).

I have no idea how or if that applies to what we were talking about. If I were me I'd take my advice with a grain of salt.

 

[pallidin]

The STM tips look downright low-tech, don't they?

Indeed, and as was inferred in the site, duplicative measurements should be consider with care due to the inherent diferrences and stabilities of STM tips.
What I would like to see, Janitor, is a concerted engineering effort to improve and standardize STM tips.
As the other elements of the system appear well-grounded, this aspect seems one of paramount importance.

 

[ArmoSkater87]

But is there an actual optical image of an atom, with the nucleus and electrons

 

[swansont]

But is there an actual optical image of an atom, with the nucleus and electrons

No. Visible spectrum photons' wavelengths are much too big to be able to image a nucleus or even an atom. Diffraction would wash out any image you might expect.