Slowing Down Atoms And Biomolecules With Lasers

Tokyokid writes "In an interview on Berkeley Groks, Nobel Laureate Steve Chu talks about cooling atoms down using lasers. In another words, the atoms or molecules are slowed down in this "optical molasses." Scientists now are using these techniques to study the interactions and forces between biomolecules. These studies may give a better understanding of how life works on the molecular level."

Comments

nope

[H4x0r Jim Duggan]

Lasers heat things up, not cool things down. Jeez, hasn't this guy ever seen a movie?

Re:nope

[ciaran_o_riordan]

The idea is that you want to reduce the average velocity of these atoms down to a very very low speed and that's what they really mean by cooling the temperatures and measuring the average motional energy of these atoms. You do this by shining light on the atoms.

As the light scatters from the atoms, they cool down. The trick is to arrange the light to preferentially scatter off of photons opposing the motion and this is done simply by tuning the frequency of the light so that when the atoms are moving towards this laser beam, it has a frequency shift called the Doppler shift that actually shifts it more into resonance.

Re:nope

[Kethinov]

The important question then, I suppose, is how cold can you get them with "light-cooling"?

If this technique were to develop well enough, it could spawn a whole new method of refridgeration.

Re:nope

[jabberjaw]

According to this, about 100 billionths a degree above absolute zero. This just turned up with a quick google and it has most likely gotten lower since then. As for refridgeration, not in the near... or distant future.

Re:nope

[NonSequor]

You know that I have no way of knowing whether or not you're just pulling this stuff out of your ass. All of this is indistinguishable from dialogue from an episode of Doctor Who to me.

Re:nope

[P-Nuts]

Lasers heat things up, not cool things down.

The energy from the absorbed laser photons is not lost, so there is a heating effect somewhere. The experimental setups are clever enough that the atoms are cooled, but since each atom in the process of being cooled reradiates as many photons in random directions as it absorbs, these are free to go off and heat things up. In a typical experiment, they will hit the stainless steel walls of the vacuum chamber and heat them up very slightly.

In case anyone is interested, thermodynamics isn't violated either. The decrease in entropy (disorder) of the cooled atoms is more than matched by the large increase in entropy of the photons, which go from being in a highly ordered coherent beam with high mode occupancy to being in all sorts of random modes with no coherence.

Re:nope

[Anonymous Coward]

You mean except for Batman and Robin?

Maybe we can use this technique

[Anonymous Coward]

to slow down Darl McBride

Note to Modders

[Anonymous Coward]

The parent comment is moronic, it applies nuclear/atomic physics to a macroscopic concept, but it gets +1 informative - and the original post in this thread, a joke gets modded as -1 troll. good night.

IANAP, but I can see that some physics comments are ungrounded.

To Kethinov: sorry about my harsh comments, but I'm right about you being a bluffer, amn't I.

Compton scattering

[aurum42]

Is this related to Compton scattering (usually between an electron and a photon)? As I recall, there's a cos(Theta) term there, so the energy transfer could go either way between the electron and the photon. This also sounds a lot like how the bose-einstein condensate (a recently discovered "new state" of matter, and cause of a nobel) was created.

Re:Compton scattering

[Anonymous Coward]

Is this related to Compton scattering (usually between an electron and a photon)?

Nope.

This also sounds a lot like how the bose-einstein condensate (a recently discovered "new state" of matter, and cause of a nobel) was created.

Yep.

Re:Compton scattering

[P-Nuts]

Is this related to Compton scattering (usually between an electron and a photon)?

It isn't particularly related, except that the ideas of quantum mechanics that are demonstrated in the Compton effect are important for understanding laser cooling.

Compton scattering is an elastic collision of a photon (usually a rather high energy one, like an X-ray) and an electron. The target electron is initially a free stationary particle.

Laser cooling involves the absorption of a photon (probably visible or infra-red) by an atom, which has been brought into resonance with that photon by a Doppler shift (and possible also a Zeeman shift in an magneto-optical trap or MOT). Therefore one of the electrons in that atom is promoted to a higher energy level. The atom stays in such an excited state until spontaneously decaying, releasing another photon in a random direction. The cooling occurs because the momentum of all the photons absorbed act to slow the atom down (or push it to the centre of a trap in a MOT), but the photons emitted can go in any direction so have no net effect.

Re:Compton scattering

[Anonymous Coward]

Youse a cracked out fizzool. Everybody knows that Compton scatterin' be when the popos send in the riot popos to crack down on the bruthas in COmpton. Then all us thugs be scattin'.

No more freezing corpses in liquid nitrogen !

[Anonymous Coward]

Finally, we can now use LASERS to freeze bodies shortly after death. Liquid nitrogen is a thing of the past. All hail our newest technocratic master, the LASER!

What's new?

[QuantumFTL]

Not to troll but... this technique has been used for years! I've seen the setups (I still remember the issue of Scientific American that had a story about this - one of the reasons I went into physics).

I guess it's not a bad interview, but was there something groundbreaking in there I missed? Or is this just one of those "it's not news, but it's still for nerds" things?

Cheers,
Justin

Re:What's new?

[P-Nuts]

Not to troll but... this technique has been used for years!

Indeed, Chu took the 1997 Nobel prize in physics along with Phillips and Cohen-Tannoudji. The Nobel site includes an illustrated presentation of how laser cooling works.

Re:What's new?

[KDan]

Agreed. I had to answer questions about this on my finals papers in my physics degree three years ago!... how is this news exactly?

Daniel

Re:What's new?

[omega_cubed]

Nope. This really isn't stuff that matters, nor is it news. Chu won the Nobel for it 7 years ago (along with Claude-Tannoudji and Phillips).

Re:What's new?

[Mark of THE CITY]

I believe it's the application of this technique to biomolecules, as opposed to individual atoms. Something as big as a protein or peptide tends to be fragile, so I'd be curious as to how they do it.

I did experiments in grad school which condensed various organic molecules into small clusters via "supersonic expansion," but that only cools to 5 Kelvins or so. Putting more molecules into lower rovibronic states would make it easier to do experiments, as you have a better defined starting point.

Re:OT

[deglr6328]

Seeing as how you're on the "inside" of this thing...care to spill on any details of what the Big Announcement will be about tomorrow?

Re:OT

[QuantumFTL]

Seeing as how you're on the "inside" of this thing...care to spill on any details of what the Big Announcement will be about tomorrow?

Well I'm not allowed to say, except that it's worth watching :-D

It's important, and it's good news. And it involves rocks. On mars. That's all I can say.

It's worth waiting for :)

Cheers,
Justin Wick

Ice beam baby!

[DigiShaman]

Damn, I hoping to have an Ice Beam in the near future. It would be nice to fight monsters like Samus.

*sigh* I really need to stop playing Metriod.

High Time

[rixstep]

I think it's high time someone thought about cooling atoms down. Those little buggers, when they get excited and hot, they start bumping into things.

Re:OT

[Bloater]

They've found a rock that looks like JESUS!

goto scientific american web site

[Anonymous Coward]

If you do a search you can find some older scientific american magazine articles that talk all about using lasers to cool atoms....if you look at newer articles (on nanotechnology web sites..), you can find that people are starting to use lasers as a form of tweasers to manipulate atoms..

Why don't they just leave...

[Anonymous Coward]

the atoms and biomolecules alone? What did they ever do to Mister Chu?

Obligatory BOFH reference

[Pantheraleo2k3]

An "ice gun" based on this could end up being the BOFH's new weapon...

Imagine a new era in document destruction. For example, aim at the "Helpdesk software backup" tape the boss is holding, and fire!

Imagine a new way to torture lusers, replacing the tried-and-true (boring) staple-gun. Especially handy when aimed at certain parts of the body. Shoot it discreetly into a Bean Counter's coffee and watch their stunned reaction

Yep, it sure is good.

it's not cooling...

[Anonymous Coward]

the only reason they think they see it slower is because it works just like a strobe light...duh.