Re: Repulsion binds atoms


Edward Green wrote:
Ken S. Tucker wrote:

Edward Green wrote:
Sam Wormley wrote:

Repulsion binds atoms (Jun 15)
http://physicsweb.org/article/news/10/6/8

Physicists in Austria have created a new type of stable bound state made
from two atoms that repel each other.

Something bothers me. <...>

Another one bites the dust.

Not necessarily, a pop-article does contain
ambiguous phrases often disguising much
more sophisticated thought, consider this
article...

http://en.wikipedia.org/wiki/Cooper_pair

Now I'll provide my intrepetation with a bit
of background first.

Given two OPPOSITE charges,

(-) -------r-------(+) , ((Energy p = ab/r = -q^2/r)),

the so-called Coulomb force operates Quantum
Mechanically by converting that to a reduced
radius r' and thus less stored energy by emitting
a photon,

(-)-----r'-----(+) ~~~~> photon, ((p' = -q^2/r' + hf)).

The key factor above is the existance of an
electrical dipole " (-)--------------(+) ".

Let's now consider two LIKE charges,

(-)-------r-------(-)

and please note, there is no dipole now.
So the question from the standpoint of either
classical EM or QM is how a photon is
emitted by an increased radius to r' storing
less energy in transition to this,

(-)-----------r'-----------(-) (fig1)

without a dipole that gives an electric field
direction?

In my humble simplicity, I figure an electric
field vector may be modelled by a (-) at the
base and a (+) at the pointy end, separated
spatially, but the above (fig1) hasn't got an
electric field vector by that definition.
Emission of radiation, according to Maxwell's
classical EM requires a partial derivative like,

&E/&t , (partial Electric/partial time),

but without the "E" in fig1, fig1 remains stable,
i.e. the Coulomb force is not functionable.

So I'd be inclined to think is the fellas in Sam's
article are using heavier particles (atoms) to
demo what Cooper paired electrons are thought
to do in superconductors.
FWIW, that's my basic understanding too.

Ok... after a brief consultation of

http://hyperphysics.phy-astr.gsu.edu/Hbase/solids/coop.html

I see that cooper pairs are electrons effectively bound by lattice
deformations, or phonons. So the apparent paradox, that
electron/electron interaction is purely repulsive, yet they form pairs
at low temperatures, is explained by the influence of the environment,
which gives a minimum of the potential in the over all system at some
separation. Electrons in free space repel, electrons in the lattice
attract over some range of distance, because the force, being minus the
gradient of the potential of the net system, is attractive.

I agree that it sounds like the heavy atoms are doing something
partially analogous to the cooper pairs, but I would maintain (because
I am cussed), that presenting this as a paradoxical "attraction of
mutually repulsive particles" is making things as strange as possible,
rather than as simple.

"paradoxical" is a characteristic buzz-word in
pop-sci articles. Anyway without studying the
actual authors article it's less than precise to
get to deep into what they've done, aside from
something (maybe) akin to Cooper pairing.

I can't resist an analogy: Say persons A and B dislike each other, and
can't stay far enough away. However, they move in the same social
circles, and have common friends, and neither can turn down an
invitation to a party. In fact, each is almost certain to accept an
invitation to a party knowing the opposite individual was invited, lest
that one have a free field to gossip about him. Because of their
environment, although in society free space their interaction would be
purely repulsive, they paradoxically seem to form a bound pair in the
party lattice.

Well a pair of protons in a nucleus is also strange,
if the strong nuclear force is not understood.

Come to think of it, no author worth his salt would describe such a
situation without dwelling on the delicious irony of how their mutual
repulsion was converted into pair formation by the social environment
-- so maybe I should be more forgiving. ;-) I was involved in a
situation like that at work, where I was forced to work with a guy who
was a duplicitous <expletives deleted>, I think in part because
management knew I couldn't stand him.

I've been lucky to get-along with everyone I've
worked with, I've fired a few, but that was due
to unsuitability. It's institutions that evolve
policies that are "duplicitous" so I've fired my
share of institutions.

I'm not sure how your no-dipole explanation figures: how do two like
charges in free space manage to increase their separation, radiating
(emitting photons) in the process?

It's quite clear a pair charges moving as,

(-) ---->----<----(+)

has a net current required for the production of
an EM-wave. However a pair of LIKE charges
moving as,

<----(-)--------(-)---->

has no net current, and hence current change,
and thereon to no magnetic field change, so I
don't know how to make that pair radiate.

I rather think QED as well as classical EM can handle this.

But then you would want to ask about
"Electron Beam Lithography" or "Electron
Microscopes". I haven't found evidence
a pair of free electrons will radiate, I'm
even thinking of a Direct Current too.
In the case of DC, without a resistor to heat,
I can't see how any radiation can occur.

Thanks as always for your constructive replies.

Welcome, thanks, it's a tough problem
for me that I've wanted to breach with others.
Cheers
Ken S. Tucker

.

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