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Atomic Orbitals Imaged
joshv writes "Ever think that physics professor was smokin dope as he described those mysteriously shaped clouds of electron probability floating around atoms? Here's proof. Someone has managed to image atomic orbitals using X-ray crsytallography." The story's from Scientific American; very cool stuff. This may be old hat to physics grads, but it's interesting to us laypeople. ;-)
The page is nice to read too, by the way.
And if you look at the Nobel prizes in Chemistry or Physics and note where the first reported mention of the work occured, I'd expect that you'd also find contrivesry as the idea was tossed around the scientific community.
Of course. There's bound to be controversy when a new theory/idea is introduced which, if true, would cause a drastic change in currently held theology in that field.
I imagine that I wouldn't be ready to jump at this new information and hold it concretely until someone else had worked on it as well, and produced the same result. Of course, I do find it intriguing, but, since I'm not an expert in this field, and I certainly don't understand the processes of which they speak, I can't throw my opinion of that around.
I just think it's interesting, but they should, if they rewrite the books, show this as a new theory, but that, as before, they aren't 100% sure that they're right.
Insert mind here.
Here is another graphics.
What is looking? Some process that gives you information on the object you look at. On the physical level this exchange of information turns down to an fundamental interaction. And those change the state of the observer and the object.
Zuo says, "Understanding bonding in copper oxides is the key to solving the biggest unsolved problem in solid state theory--the nature of high temperature superconductivity in copper oxides."
Does this have anything to do with the Copper interconnect process being used by IBM, Motorola, and (next year) AMD?
Queens of the Stone Age - they rule
But where do the choices come from? Is it a result based on some physical states somewhere (like a computer program that takes a certain decision given a certain input) then it is determined, the opposite seems to be something truly random, so we can't speak of a decision anymore. Does not fit into logic, in my opinion.
In the sense of Hofstadter I would say that we have no chance to solve these issues until we understand what a "self" is and find some mathematical (thus logically consistent) model for it.
But the wavefunctions evolve deterministically (Schroedinger's equation etc).
This is true, but worthless, because the wavefunction can never be known (and is complex). All that can ever be observed is the square of the wavefunction, the probability distribution of the quantum state described by the wavefunction. If you think about this for a bit, you realise that this prevents you from ever being able to make any predicitions at all using QM.
Quidquid latine dictum sit, altum viditur.
To temporerily sacrifice _enthropy_ for the pursuit of _entalpy_*. Now did that destroy your life? No? What if i say that the world IS determenistic? I mean... so what? I've belived those things since i was 11 and i still belive i have a purpose in life it's... well...(see above) but anyway you don't really need one of those high-minded filosophical purposes of life kinda things to live your life.
*) Maby it was NON-entalpy, i always get that wrong.
LINUX stands for: Linux Inux Nux Ux X
FRA: STFU GTFO
What I see in your image is a 2D density image. The "new" story has 3D reconstructions. Gives a whole new dimension to the whole thing....
Roger.
To be truthful, probably 99% of the physists out there are either doing the work at the quantum level (and thus can be called physical chemists), or work at the extreme macroscale (that is, universal scale), and thus can be called astrophysists.
Almost everything in between was solved by Newton way back when, and Einstein in the early part of this century, except for the connection between a 'small' number of molecules (on the order of 1 to 10^10) and the quautum theory level. And that's the job of chemistry :-)
"Pinky, you've left the lens cap of your mind on again." - P&TB
"I can see my house from here!" - ST:
The problem we have here is that we try to extrapolate a statement from basic physics, from very simple, idealistic situations, like the path of a particle to very complicated situations, like the free will of an intelligent being. Very easy to be victim to improper generalization.
Example: I am able to write a program for a computer, that pretty much gives determined output, despite the fact that all particles making up my box are subject to the Heisenberg principle.
Of course a cosmic particle might flip some bit, or all particles (and thus my box) might show up on Mars in a second, that is all perfectly legal under present known laws of physics, just extremly unlikely.
Awww..corruption at the foundation of our educational system is no big deal. Seriously, that was a bitter pill for me to take when I was at college. Seeing dozens of revisions on topics like ancient history etc made me a angry. They pay off the profs to get the new texts used so they old texts become worthless. They have to make changes to make each revision seem legitimate. What you end up with after a few of these cycles is literary trash. Information may still be there but is painful to read.
Thus, I suspect that the details in this SciAm are about as deep as they are in the Nature or Science article, just rewritten to a slightly lower reader level (not too low, mind you, just low enough for the scientific layman to understand). Yes, you should expect contriversy about it. If I remember correctly, the Cold Fusion project of years back underwent a similar treatment. And if you look at the Nobel prizes in Chemistry or Physics and note where the first reported mention of the work occured, I'd expect that you'd also find contrivesry as the idea was tossed around the scientific community.
Now, there is one last point: both Science and Nature are what are known as peer-reviewed journals: before you can publish in those, your article is subjected to critism from at least 3 experts in the field (these experts are anonymous). If they find something fishy or questionable, they'll ask you to fix it , or not approve the article for publication. The fact that it DID get published means that at least 3 experts agree with the results and how the researchers got to them. However, another cavaet - from a chemistry standpoint, this result makes me want to shout horray, as it proves something that's only been shown to work in theory. It's rather easy to ignore possible problems in the mechanics of the experiment for a result like this.
However, now that the technique is out there and reported, you'll see others trying to repeat this, and within 6 months, we'll know if we have the next cold fusion, or the next Nobel-prize winning award.
"Pinky, you've left the lens cap of your mind on again." - P&TB
"I can see my house from here!" - ST:
For a different take on uncertainty and related matters, I recommend reading The Transactional Interpetation of Quantum Mechanics by John Cramer at the University of Washington.
One of the things that this paper made me wonder about is the implications of the exitence of the present moment. It seems to me that the simplest reason for there being a present moment is that the future is in some sense indeterminate. Whether this means that we have free will or not is an open question (could be only God does or everything could be random and we are rats in the maze) but worth considering. At any rate, the fact that we can percieve the present moment to me argues strongly that we are active in it. If this is really the way that reality is structured, I would be very leery of someone claiming that evolution would not find it and make use of it.
The situation may even be more subtle than my poor description above. Suppose that the future is inteterminate but constrained in some manner. The present moment might not be a point but have some sort of width described by a Poisson-type weighting and different possible futures get to vote, but the further out you go the less say a future has. One of the possibilities opened up by this model is some variation on Teilhard de Chardain's infamous "Omega Point" teleological God.
This model of cognition may also allow us to appreciate the concept of infinity by doing an infinite number of back and forth transactions in a finite amount of time. Sort of what Penrose was trying to say, but with a somewhat different mechanism.
Anyway. I am a mathematician, not a philosopher or a physicist, (although I play one on TV, much to the chagrin of my brother the experimental physicist!)
You will not drink with us, but you would taste our steel? - Walter Matthau, The Pirates
I agree. Another area that I think is important is the expansion of the Universe. If it were possible for "someone" from outside our own Universe to control the nature of little bits of reality popping into existance it would allow them complete, omnipitotent control. This assumes that they can predict with high accuracy the effects in chaos.
For example you are trying to decide a particular model of car to purchase. This mysterious someone used their skill to slow down a cosmic ray, 10 years ago. That cosmic ray passes through your brain, lights up a neuron (ok, simplistic here) and changes your decision.
While convoluted, to a lay person such as myself, it appears possible. Between this and the Uncertainty Principle (Which I believe proves that any Supreme Being must live in annother Universe, because I don't believe in Supernatural powers)
Any thoughts, takers?
-- Remember: Wherever you go, there you are!
Orbitals are NOT observables! Differences
in the electron density, which is an observable,
were found to LOOK like an atomic orbital. This does not mean that orbitals exist. They are mathematical entities that most chemists,
and even some physisists take way to seriously.
With all the hoopla about density functional theory, it's sad to say that most chemists still think that orbitals are somehow real. This may
seem like semantics until you realize how much
NSF money goes to support this sort of thinking.
I dunno. I don`t think it`s necessary to invoke the uncertainty principle. It`s sufficient that there are so many atoms doing so many things that it`s a chaotic system. Is there a difference between not knowing what the cause is, and saying `That electron did that because it wanted to`?
The photograph wouldn't look like the picture.
I've seen Xray diffraction photos and they are
just symmetric dots.
Just a guess here but I think the data
they used was mined from a special set of
diff photos. You wouldn't be able to see
any of the info they speak of without the
aid of a computer.
Seems very interesting.
Actually, quantum mechanics has little to do free will (or the mind in general, Penrose, et al's beliefs aside). There has been a great deal of discussion about whether quantum mechanics allowed for a 'cheat' to recover free will, usually structured around the synapses. The theory is that you can sneak uncertainty into ion channels, then add a little nonlinear dynamics and get free will.
IMO, and that of others, this simply doesn't work. It assumes that (1) quantum mechanics is complete and correct, which is far from proven, (2) that for some reason statistical smoothing doesn't happen in synapses, (3) these variation are amplified, due to the 'chaotic' nature of the brain, and (4) that randomness == free will. To be honest, I see no evidence that this *could* work. OTOH, this may be a good thing.
Free will, as most people define it, is about making free choices; that is, being able to choose one alternative over another. By its very nature, this isn't 'free' in the same way that electrons are 'free'. My choices are determined by who I am, by my ethos, my history, my culture, my beliefs, my passions. They aren't random selection, but utterly determined expressions of my will.
What you are looking for is pure freedom, but the only way to find that is to abandon everything else we believe about freedom: that we make choices, as opposed to selections simply being 'made' on their own. Heidegger wrote about this in Being and Time--I don't have it handy, but his point, IIRC, was that the more we understand Being, who we are, the more we understand how valuable, even wonderful, that psychological determinism is: it makes our choices ours, and gives them meaning and purpose.
Physics is a human concept and a concept is deterministic by nature. Freewill is also a concept, and what is undetermined can not be determined. I don't know how to define freewill so I really don't care about it.
Can't judge the state of computational chemistry. I have not heard of any big success stories.
Physicists however, especially particle physicists, depend very much on computing.
Or engineering. I did finite element modelling for solving heat diffusion problems, where computations save lots of money because it is cheaper to find out at the desk that some casting of a gas turbine blade won't succeed than after doing this for real with a furnace etc.
I saw computer illustrations but no PHOTOGRAPHS of these things.. Where? I SAID WHERE!
-Oy Vey
free will is the ability to have a pizza at 3am.
I believe that some BIG success stories in computational chemistry are just over the horizon. Chemical and Engineering News had an article several months back (April 26, 1999 p. 24) about the use of computational chemistry as a Chemical Engineering tool.
Also, take a look at this article about modeling SiON chemical vapor depositon on the Molecular Simulations, Inc. (MSI) web site.
Well, they may not have been in this work, but X-rays certainly can be focused. See, for example, the Chandra image of Cas A.
It doesn't get much more focused than that!
Yes, this frustrates the heck out of me. My thesis involves STM/AFM and I'm looking at orbitals on a daily basis. I grant that they may have a higher resolution but they definately are NOT the first to image orbitals. This kind of reporting makes my skin crawl. Charles Anthony Peterson Graduate Student of Physics at the University of Arizona capeters@physics.arizona.edu Office:(520)621-9558 Home:(520)881-6605 http://nanoscope2.optics.arizona.edu/
Chemistry has always been, like physics, based around creating a model that generally gives the correct result within a couple of decimal places, but isn't strict enough to approximate real behavior without breaking down.
;)
And now, like physics (and relativity) someone has the means and the technology to find out the truth, and force those lazy professors to rewrite the books and think again.
Man, I'm glad I'm in computer science, and can contribute to the 'means and technology' side without having to think too much.
pb Reply or e-mail; don't vaguely moderate.
I don't get why this is so new (excepting the technique possibly) I was able to demonstrate the shape of orbitals in graphyite using a Scanning Tunneling Microscope last year. Click here to have a peek yourself.
Obviously, graphyite is a typo. I meant graphite.
(I forgot to add :-)
The X-ray and electron beams are not combined, they are collected separately, and the information is combined.
Moreover, the principle difficulty has been completely ignored. Electron beams can be focused to produce a direct image. X-rays cannot be focused for imaging purposes (although crude focussing to concentrate a beam is just possible). As a result, you only get a diffraction pattern with no phase information. The image must be reconstructed by Fourier transformation, which needs the phases. (There is a strong analogy with optical holography, in which a reference beam must be interfered with the diffracted beam to obtain phase information, but with x-rays the coherence length is too short to get a reference beam).
The trick is to use the phases from the low resolution electron image, and some mathematical relationships to reconstruct the missing phases in the high resolution image, which will show your electron orbitals. The problem is unless the statistics are treated very carefully, all you get is an image which confirms the assumtions of the model you used to get the relationships with which you reconstruct the phases.
The mathematical techniques were just coming on line in X-ray crystallography in 1996 and there was still considerable debate back then over their correct application. So there is a fair possibility that these results are correct, but I would suspend judgement until they have been scrutinised for a year or two.
Mm!
Although it does not show the same detail as the results in Scientific American (and by no means is the experiment I did a novel thing - it was practically the first thing done after the STM was invented) it does demonstrate something about the shape of orbitals; namely that the electrons are not just aranged spherically around each atom.
It can be seen that the hexagonal arrangement here includes a maximum at the centre of each hexagon - this would not be observed if only spherical orbits were present.
disclaimer - I was not trying to suggest that this experiment (a tiny part of a third year project at uni) was comparable to that of the scientists in SA - only that theirs is not the first experimental evidence of orbital shapes. That much was done many years ago.
That such a treatment is possible, is not obvious, nature could have been that way, that one had to treat the whole system (like solving the wave equation for all particles at once) in order to make any useful statement at all.
Read this article on Atoms in Molecules by Richard Bader to find out more.
Bader claims that the study of the Laplacian (2nd spatial derivative) of the electron distribution leads to a natural spatial decomposition of a molecule.
Have a look at these great pictures for some simulations based on that AIM theory.
I am still surprised, that during my physics studies, I heard nothing about that treatment. You get exposed to Feynman of course, but Schwinger's formulation of quantumn electro dynamics I knew only as possible but not practical alternative. Very interesting to see Schwingers approach at the heart of this AIM theory.
In classical mechanics one learns that the conservation of energy is a consequence of a corresponding symmetry, here the invariance of the system under time (= it should not matter if you do the experiment today or tomorrow).
Thus looking sharply, energy can't be conserved througout the universe, because the universe changes.
I wonder if cosmologist take such effects into account in their models.
As the article states, electron orbital clouds have long been used to explain chemical reactions mathematically. Now, it says, they have a physical application as well. However (while not a physics major) I believe the key philisophical question is still unanswered. For those of us who do not believe in any sort of God (or do not feel the idea of God is necessary), materialists, the question we are left with is what governs our everyday activity. Is there free will? Is everything cause and effect? With enough understanding can we eventually be able to determine everyone's future?
The answer for me has always been found in Heisenberg's (sp?) uncertainty principle. He states that you can never know the velocity and the position of an electron at the same moment. What this means to me is that no matter how deep or how complete our physical understanding is, there will always be some bit of uncertainty, if only on the minutest level, that allows us to operate as if we had free will. To me, free will is necessary for me to view my life as a worthwhile pursuit.
Thus, while we can now picture the movements of electrons physically, in doing so, we disturb their velocity and Heisenburg's uncertainty principle is still valid. Therefore, while this may have increased our understanding of the universe, it has not destroyed what I feel is the basic necessity for the pursuit of life: free will.
14 digits of Pi are all we need.
The particles don't have precise Newtonian position and velocity. But that is not because the particles are not deterministic, it is because the Newtonian idea of infinitely fine grained space doesn't match reality.
Instead of space being made up of completely independent points, at the finest scales there is considerable mutual information between a point and it neighbours. So it no longer makes sense to speak of an event or a particle at a point -- what's going on at that point shares information with what is going on nearby. That's why particles are described by spread-out wavefunctions (and why the universe has a smaller information content than it first appears, with Heisenberg's equation connecting the local information density/resolution to how much mass or energy there is around).
But the wavefunctions evolve deterministically (Schroedinger's equation etc).
(Note: quantum 'measurement' events don't actually represent abrupt changes in reality -- they represent abrupt changes in our modelling of the rest of reality, of which the particle is not independent. So our modelling of the uncertainty about the particle must also change abruptly.)
Quantum mechanics doesn't have the indeterministic evolution you wanted. But even if it did, that still wouldn't give you free will. If every action you took in a Newtonian universe was conditioned on the roll of a die, that would be indeterministic, but you wouldn't have free will. The die would be in command.
On the other hand, if Laplace's calculating god could know the position of everything in a Newtonian universe apart from the material contents of your head, there would be no predictability. The unpredictability that 'you' impose on the rest of the world is your true freedom.
Once you get to that point, you're not so far from any other methods for solving the equations.
The more important issue is that the variational conceptual perspective is equivalent; but does it actually help the thoughts ?
my professors smoking dope because the way it was worded. But I have proof of that anyways, I smoked up with one over labor day.
And this is, of course, the nub of the matter. Because a being that does not believe in free will is unlikely to survive, we could have simply have evolved the whole 'consciousness' memeplex without it actually having to exist.
Or maybe not. Maybe it does exist. Maybe it's something to do with quantum effects. Dunno.
So, for now, we get on with living, yeah?
Okay...
--
The point surely is that if we consider interactions between atomic orbitals slowly being 'turned on' as a perturbation (the infamous hypothetical black box controller), then there are strong interactions between say orbitals on adjacent bonding atoms. The independent atomic orbitals are a approximation; so it is very sensible to think of joint orbitals, representing chemical bonds or functional groups.
Going to the next level, we can now (conceptually) allow the functional-group orbitals to become aware of each other. This means further interactions, so a truer picture (at least at the level of a single electron linearisation) is that the molecule has molecule-wide electron orbitals. But in practice these interactions are much weaker, so taking them into account via the full quantum mechanics makes little difference to the overall electron density distribution.
Also, although the molecular orbitals are the right solution for a well isolated molecule doing its own thing, in practice chemists are often more interested in reactions & mechanisms. These involve applying local perturbations to the electrons' environment which are much stronger than the comparatively weak interactions between the groups; so taking group orbitals as a conceptual base is a better and more appropriate first-order approximation than molecular orbitals.
But in other cases, Molecular Orbitals are the more useful conceptual approximation -- eg for thinking about electron transfer between different levels, which is the basis for the beautiful biological miniaturised electron tunnelling spectroscopes that give us the sense of smell in our noses.
For all you know, G-d might have some way of looking at things that doesn't involve bouncing light off them. If we figure out such a way, then we'll have made some progress.
"If one is really a superior person, the fact is likely to leak out without too much assistance" -- John Andrew Holmes