What is the sound of one excited atom ? ... now we know. Wow.

[cbelt3]

http://motherboard.vice.com/read/scienti...atom-makes


Wow. A 'phonon'....

[August West]

Cool

[NewtonMP2100]

thought it would be....yippee....!!

[eustacetilley]

Where to begin...

In Physics, one of the most confusing terms that one comes across is "Phonon". It's a lousy term, almost as bad as "Spin".
(The Wikipedia article is nearly worthless; it is pretty much all theoretical, and ignores much of the experimental work done in the last few decades. The Talk section is actually pretty good.)

A single "Phonon" is a curiosity. (The paper admits as much.) Where Phonons come to play is in Collective Action; that is Conduction, from one place to another.
Simply, very simply, phonons conduct Heat, by Mechanical Vibration. These Vibrations have Frequencies, typically starting in the GHz region, and up. This is done in a "stepwise" manner; Phonons are a kind of Quantum Particle: "Quasiparticles". (Phonons have no physical dimensions, or any Mass, in conventional terms.)

So what does all this mean? Take your first Semester course in Classical Electrodynamics: You get introduced to Particles, Waves, and Frequencies, and just enough Quantum Physics to pass a test.
When it comes to what you hear and can pick up on a Cellphone, concepts of Waves are good enough, and Particles can be ignored. When you are counting Gamma Rays from Nuclear waste, individual Particles are just dandy, and Wavelength is immaterial. (It can be measured of course, that is what Gamma Ray Spectroscopy is all about.)
Now stick a Copper Spoon into a cup of hot tea. Energy is certainly conducted; your fingertips tell you this. But not at anywhere near the Speed of Light. (This is where I should use a Car analogy, but screw it.) Energy in the form of Photons get into the spoon, gets converted to Phonons, and at some point leave the spoon- as Photons again... slowly.

Phononics isn't anywhere near being ready for practical Applications, other than the ones that we are already used to. But Superconductorists are very interested in Phonons, it sort of gives them a Purpose in Life, a Goal: Phast Phonons.

Eustace
(Hey, I did this with no Math, and only one Huge glaring obvious mistake!)

[NewtonMP2100]

but if no one is there to hear it.....does it make a sound.....???

[Wags]

NewtonMP2100 wrote:
but if no one is there to hear it.....does it make a sound.....???

What about that guy's cat?

[space-time]

Now stick a Copper Spoon into a cup of hot tea. Energy is certainly conducted; your fingertips tell you this. But not at anywhere near the Speed of Light.

I did the opposite: in one of the CO2 laser I did many many years ago, we used a Diamond as the exit window. It was a 30 mm by 8 mm rectangle, roughtly 0.5 mm thick. It was artificial diamond. If you held this in your hand, and tried to cut ice, it was like cutting butter with a knife. heat from your fingers was flowing through the diamond into the ice. The diamond conducts heat better tnan copper, I forgot the exact numbers but I think it is much better.

[eustacetilley]

space-time wrote:
Now stick a Copper Spoon into a cup of hot tea. Energy is certainly conducted; your fingertips tell you this. But not at anywhere near the Speed of Light.

I did the opposite: in one of the CO2 laser I did many many years ago, we used a Diamond as the exit window. It was a 30 mm by 8 mm rectangle, roughtly 0.5 mm thick. It was artificial diamond. If you held this in your hand, and tried to cut ice, it was like cutting butter with a knife. heat from your fingers was flowing through the diamond into the ice. The diamond conducts heat better tnan copper, I forgot the exact numbers but I think it is much better.

Much, much better, thermal conductivity, especially at Cryogenic temperatures, and that combined with its excellent electrical insulating properties, (When it isn't excellent is where things get interesting...), makes Diamond The Choice for those that can afford it. We couldn't, so we used Ruby or Sapphire windows for our ECR Klystrons. ¹²C Diamond is some eight times a better thermal conductor than Copper:
http://en.wikipedia.org/wiki/Material_pr...of_diamond

When I was introduced to Phonons at a tender age, they were a Theoretical Mathematical Convenience. Thirty years later, the damn things were everywhere, largely because of the Superconductivity thing. In those thirty years, I had occupied myself with much heavier boogers, and I got a rude awakening- the thingies actually exist, and can be measured to a certain degree, and I had better get up to speed.

I may come across as a Luddite on certain issues brought up here. (It's all those tiresome essays on Etymology, Ferraris, and Irish Cuisine I suppose...) I actually prefer the tried-and-true when it comes to simple Engineering, and I no longer care for the State Of The Art in those areas. (The Cost of Admittance is merely keeping up.)
So I just jump right over it to the cutting bleeding edge- things never seen or heard or thought of right up to Now. To paraphrase Feynman, (Maybe), on the Science of the Manhattan Project: "We already know the Physics. The rest is merely Engineering."
Phononic Research is complex and expensive, given our primitive tools. But any Kitchen Scientist with access to Liquid Helium and only a few kilobux of instrumentation can investigate some Phonon-related oddities, like why does the Thermal Conductivity of Nickel vary so much from sample to sample at Cryogenic temperatures, and why the sea is boiling hot, and whether pigs have wings.

Eustace

[DP]

Eustace, do you actually have a copper spoon?

[m.paris]

"The Cost of Admittance"

Is that a slip, a pun, or a test to see who is paying attention?