Science News

Electrons are spherical

Wed, 25th May 2011

Chris Smith

What's round and measures a billionth of a millimetre?

The answer is the electron, the shape of which scientists at Atom structureImperial College in London have been trying to measure for over ten years! Now they've finally succeeded, proving that the tiny negatively-charged particles which swarm around the nuclei of atoms really are a spherical shape.

Led by researcher Jony Hudson, the London-based team made the breakthrough by studying how a compound called ytterbium fluoride behaves in an electric field. If electrons are any shape other than perfectly round, then in an electrical field they would be expected to wobble and this, in turn, would make the ytterbium fluoride atom wobble too.

But if the electrons are spherical, then any forces will on them will balance out and so they won't wobble and nor will the host atom. And, in fact, this is what the team at Imperial have published this week in the journal Nature - the atoms failed to wobble in the field, indicating that the electrons must be symmetrically round.

This is important, explains Jony Hudson, because it places limits on what theories of atomic structure and behaviour are possible. It also moves us one step closer to answer one of the Universe's biggest questions, which is where has all the antimatter gone?

Theory predicts that matter and antimatter were made by the Big Bang in equal measure, but wherever we look today all we see is material made from matter. The shape of electrons constrains how matter and its anti-matter equivalent can behave and therefore narrows the range of possibilities of where the antimatter might have gone...

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So how does this square with string theory; that electrons are actually string-shaped? Does this invalidate it? Or are our experiments just not sensitive enough to tell? Supercryptid, Thu, 26th May 2011

The article doesn't explain how they determined the shape or even how they define the shape. I expect that the electron should fill a spherically symmetrical space at ordinary time scales, but at the Planck time scale, its shape will probably never be detected directly. We can only infer the shape from our models; and for now, mainstream science models don't even speculate about time and space at the Planck scale. The prevailing attitude is that what can't be measured doesn't exist.

Even the orbits of solar systems precess; if you fast foreward by a factor of several trillion, you will see the planets filling spherically symmetrical clouds. The orbits of electrons around atoms fill such probability-distribution clouds at time scales down to about 10^-18 s. If we could observe the interior of an electron, it probably would fill a similar, but much smaller cloud at a time scale of 10^-24 s. We would need a super collider bigger than our solar system to observe smaller scales than that; so it probably will never happen.

Outside the mainstream, there are various proposed models. Go to the New Theories section of NS to discuss these. In one model, the electron has a spiral toroid shape.

In my own model all known particles consist of more fundamental particles, which consist of orbiting pairs of photons (held in orbit by the Higgs force). I don't know if the electron is fundamental, or if it consists of orbiting pairs of fundamental particles. There could be several orders of complexity between fundamental particles and electrons, for all I know. Phractality, Thu, 26th May 2011

You make eminent sense there Phractality. I too would assume that a electron should be a 'symmetric' solution if we could 'pin point' it, which we can't. They made a calculation on its symmetry it seems to me, translating that into a 'shape'? Very smart :) and possibly correct but no guarantee for what a 'electron' really is. yor_on, Thu, 26th May 2011

From the published paper in Nature:

"Pulses of YbF molecules are emitted by the source17. The experiment uses those molecules in the F50 and F51 hyperfine levels of the ground state. The molecules pass through a first fluorescence detector, the pump detector, which simultaneously measures and empties out the F51 population. Then they enter a pair of electric field plates, between which are static electric and magnetic fields E, B^z, where ^z is the unit vector in the z direction (Fig. 1). This region is magnetically shielded. A radio-frequency (r.f.) pulse is applied. The
molecules then evolve freely for a time T, during which the mF561 components develop a phase difference of 2w52(mBB2deEeff)T/B, where mB is the Bohr magneton. This is due to the Zeeman shift 1mBBmF (ref. 18) and to the EDM shift expressed by the effective interaction 2deEeffmF (see Methods). A second r.f. pulse is then applied, resulting in a final F50 population proportional to cos2w, which the second fluorescence detector subsequently measures. For every pulse of molecules, the time-resolved signals from the pump and probe detectors are recorded." chris, Thu, 26th May 2011


You need a PhD to comprehend any of that. I wonder if "m" stands for "mother" and "BB" for "big bad". Phractality, Thu, 26th May 2011

shaped like an egg? which came first, electron or egg? CZARCAR, Thu, 26th May 2011

OK, here's the PhD free version
"If electrons are any shape other than perfectly round, then in an electrical field they would be expected to wobble and this, in turn, would make the ytterbium fluoride atom wobble too.

But if the electrons are spherical, then any forces will on them will balance out and so they won't wobble and nor will the host atom. And, in fact, this is what the team at Imperial have published this week "

which looks clear enough to me. Bored chemist, Thu, 26th May 2011

http://www.bbc.co.uk/news/science-environment-13561876 CZARCAR, Thu, 26th May 2011

Did they discover the electron's shape or an electron molecular orbital's shape? lightarrow, Thu, 26th May 2011

In a sense the orbital represents the electron, doesn't it? The probability density is symmetric until you stop 'time' by your measurement, forcing it into a outcome.

ahem :)

It's a nice question Lightarrow :) yor_on, Thu, 26th May 2011

Symmetric but not necessarily spherical:
http://www.sciencephoto.com/media/2208/enlarge

and however the orbital's shape doesn't depend on the electron only, but on the interaction with the nucleus and the other electrons. lightarrow, Fri, 27th May 2011

There are hints in various papers that this discovery leads to an advancement in our understanding of CP violation (and hence the imbalance between the amount of matter and antimatter). Can anyone explain how? I can see vague reasons how it maybe related, but I'm sure it must be something specific. graham.d, Tue, 31st May 2011

And how would it explain the electrons ability to be superimposed at two orbitals, simultaneously? yor_on, Tue, 31st May 2011

It's just an idea, I'm not sure at all: since they talk of measuring the electron's electric dipole moment, if it has, then it can be paired with the (existing) magnetic dipole moment in a different way, compared to the positron and this would mean a different energy of the particle. I can have written a stupid thing, however... lightarrow, Tue, 31st May 2011

I don't know what I should see a orbital as Lightarrow. Looking at the Swedish attosecond movie you can see it as having a circular shape, but as there also is a probability density to it, I'm not sure at what I'm looking at there. It's made using a stroboscope with several overlapping photos taken at extreme short time durations. "One attosecond has the same relation to one second, as one second has to the age of the universe"  In Swedish, but with the movie.

It's weird.

What you referred me to seems to be computer models. "An electron orbital is a region around an atomic nucleus (not seen) in which one or a pair of electrons is most likely to exist. Four of the five 3d orbitals are made up of four lobes, centred on the nucleus. The orbital at lower right is bi-lobed with an encircling ring. They are part of the 3 shell, which also contains one spherical 3s orbital and three bi-lobed 3d orbitals, both at a lower energy (not seen). The 3d shells are partially full in the first row of transition metals. These metals typically form coloured compounds as electron transitions between 3d orbitals absorb some visible wavelengths of light."

But they don't fit the 'movie' as it seems, so the representation has to be another.
yor_on, Sun, 12th Jun 2011

There's all the difference in the world between the shape of an orbital ( which is different fro different atoms, molecules ions or even different excited states of a given atom) and the shape of an electron.
Bored chemist, Mon, 13th Jun 2011

... and they measured the electron "shape," an intrinsic property of the electron itself, not the orbital's shape. jpetruccelli, Mon, 13th Jun 2011

So we found that it is a defined particle then?

yor_on, Tue, 14th Jun 2011

They found it's "perfectly round."  They could test to see if it wasn't a perfect sphere and that test came up negative to a high degree of precision.  They managed to test despite the fact that it was in an atom. jpetruccelli, Tue, 14th Jun 2011

Let's see. We got a probability density over where it should be, but only before a measurement, and then we got a definition of 'something' in that orbit(al) that's perfectly round :)

So, knowing that, should we start calling it a orbit again :)
==

But it doesn't explain how a electron can be seen as being in two orbitals simultaneously.
At least not to me.

Superposition.  yor_on, Tue, 14th Jun 2011

The orbit's got nothing to do with this question of electron shape though.  I'm assuming they carefully controlled for that in the results.

The thing is that something perfectly round that has an electric charge reacts differently in an electromagnetic field than something that's not round, and it sounds like that's what they tested for. jpetruccelli, Tue, 14th Jun 2011

This one is worthy of a long thread of its own methinks.
But yeah, that makes sense. It's a property of the electron. yor_on, Tue, 14th Jun 2011

Anyway, the fact an electron has electric properties with spherical symmetry, doesn't mean it is a sphere, of course (just for people who could think that...)
An electron is not a ball, but a wave, in case. lightarrow, Tue, 14th Jun 2011

:) yor_on, Tue, 14th Jun 2011


The experiment showed the wave to be ball shaped. Bored chemist, Tue, 14th Jun 2011


The experiment showed the wave to be ball shaped.
It could be. But I'm not totally sure. I would have said that an electron has not an intrinsic shape but that it depends on the wavefunction's symmetries. Let's take an electron inside a metal box; I would have said the electron takes all the box' space. lightarrow, Tue, 14th Jun 2011


The experiment showed the wave to be ball shaped.
It could be. But I'm not totally sure. I would have said that an electron has not an intrinsic shape but that it depends on the wavefunction's symmetries. Let's take an electron inside a metal box; I would have said the electron takes all the box' space.


Yes, lightarrow, you've said it best of all. The electron is really just a tiny zap of probabilities defined by some wave function state on the system Ψ. If it has a structure, it's made of the same stuff as the wave function - only that when the electron is not being observed, it spreads out over space; this may be a physical quantity, but only up to a limit - or it may be completely physical. I say this because we have observed multiple quantum physical states without disrupting the wave function on the system, so it seems it smears over space in a physical way, either for so long, or all the way into infinity! Hard stuff to imagine, even for me. Mr. Data, Sat, 2nd Jul 2011

A standing wave in a cavity huh :) And atoms are even bigger standing waves, and a molecule is a he* of a lot of standing waves, that moves too :) And humans are he* of a he* of a lot of standing waves, in a countless amount of cavity's, that also posses a will, free or not, that even allow them to choose directions in which to move :)

And that explains it?
ahem?

(couldn't resist it:) yor_on, Sun, 3rd Jul 2011

The electron's wave function takes up the whole box (actually, in the 1st excited state the wave function has a value of zero in the middle of the box and so on) but the electron is still a small thing which has, according to the original article, been shown to be small and spherical.

"it's made of the same stuff as the wave function"
It doesn't even have the right units for that to be true. The probability density is proportional to the square of the wave function.
Whatever units the wave function has they must differ from those of the probability distribution.

Bored chemist, Sun, 3rd Jul 2011



No I don't mean dimensions. Or units. I mean it in the literal sense; an electron, truely is nothing but a speck of probability which would inflate to giant sizes in the fraction of a second. It doesn't of course, most likely to do with it's environment. Mr. Data, Sun, 3rd Jul 2011

What they have proved is the fact it has zero electric dipole moment. Now, the say (implicitely) that this fact means "the electron is spherical". Ok, now the question is: what does "the electron is spherical" actually means?

Another question: what does "the electron is small" means? "When" or "where" is small? If I collide a very fast electron against a proton I can compute the scattering as if the electron were a point, because the interaction has that property. But even the planet Earth can be considered as a point in the gravitational interaction with Saturn; clearly it depends on the physical system and situation we are considering. Can we say the Earth is point-like in the interaction with the Moon or with a little stone near its surface? Certainly not. In a similar way, can we say the electron in the hydrogen atom is point-like? No, because we wouldn't find the correct solution and so the correct orbitals in that case.

You say  the electron wavefunction is a thing and what "the electron is" is another.
For what I have understood till now and of course I cannot pretend to know the subject better than those scientists, you cannot make that distinction: or the electron "is" the wavefunction (but just a few physicists hold this interpretation) or you cannot say what it is at all. lightarrow, Tue, 5th Jul 2011

"No I don't mean dimensions."
Clearly, or you would have got them right.
"Or units"
Almost a sentence there.
Seriously, you can't say they are the same thing if they don't have the same units.
"I mean it in the literal sense; an electron, truely is nothing but a speck of probability which would inflate to giant sizes in the fraction of a second."
"Literally" what?

" nothing but a speck of probability"
Probability of what?
"which would inflate to giant sizes in the fraction of a second"
Would, in exactly what circumstances?
Obviously not ones that matter because I can localise electrons quite well. The one that was a beta particle that made my geiger counter click was somewhere in the GM tube. It wasn't hiding downstairs. It wasn't spread out across the universe. It was manifestly in the tube.
It has a probability distribution that covers the universe but, at a give time (within some error margin) it was in a given place (also within an error margin).


There is a probability distribution for me. It's largely at home, a fair bit of on the way to and from work; even more of it is at work. There's a bit of it near some pubs too.
But you can't say that this contour map of p(bored chemist) measured in units of something like reciprocal cubic metres is me. It's a property of me.
Bored chemist, Tue, 5th Jul 2011



Clearly, or you would have got them right.

Glad you have faith in me.

As for the rest, quantum mechanics is a theory of probability. Yes, an electron has a mass. Do you know what mass really is? Did you know mass is nothing but a behaviour... it is a spontaneous symmetry breaking in fields of equations that would normally conserve symmetry for massless fields. Mass a unit of measurement, but that measurement is restricted by probability. True Eigenstates of mass arise under the collapse of the wave function, as you have already mentioned, the probability amplitude. Notice that whilst we have said that the electron has a mass, it actually may as well be said to exist in a cloud of probability rather than having a real Eigenstate, only under the condition of the wave function collapse do we then consider it as a measurement.

What did you think was meant by an electron is nothing but a speck of probability?? This is so true from a quantum mechanical sense. Mr. Data, Tue, 5th Jul 2011

This is the extreme point of view of Quantum Mechanical non sense... Though QM is widely right from another point of view.

Look in Lighter - New Theories section for my explanation. CPT ArkAngel, Wed, 6th Jul 2011

I thought that I held the prize for the most unanswerable useless question by asking how "many Angels can dance on the point of a pin" but now I feel I have been relgated to second place. syhprum, Wed, 6th Jul 2011

i like to sprinkle atoms on my pasta at the university dont they make them in france or something dr thompson, Wed, 4th Sep 2013

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