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Eric Cornell and Carl Wieman created the first BEC, using a combination of laser and magnetic cooling equipment. They created a laser trap by cooling about 10 million rubidium gas atoms; the cooled atoms were then held in place by a magnetic field. This can be done because most atoms act like tiny magnets; they contain spinning charged particles (electrons).

This is my field (I'm a grad student), so I can't resist being a little picky about that description... It's not the magnetic field that holds the atoms up, exactly.

The thing is, there are laser beams shining on the atoms from all directions, above and below, left and right, in front and behind. When the atom is exactly in the center of the chamber it won't absorb any of those beams (much). They aren't at its resonant frequency. But if it moves away from the center, maybe to the left, it starts to feel a magnetic field. This shifts its energy levels, making its resonant frequency closer to the frequency of the laser. But it also shifts those levels in a particular way which causes the atom to be able to absorb light only of a *particular* polarization.

This means the farther the atom moves to the left, the more light it will absorb, but from the rightward-pointing laser beam (to which we've given the correct polarization) *only*. And as it absorbs light from the rightward-pointing laser beam, it is pushed, back toward the center of the trap. Finally, when it gets there, it no longer absorbs the rightward pushing beam any more. There's no magnetic field at the center, so the atom's energy levels revert to their original form, and that rightward beam is no longer resonant -- nor are any of the others.

But if it tries to move up, the magnetic field makes the downward-pushing beam resonant, if it tries to move forward, the magnetic field makes the backward-pushing beam resonant, and so on.

That's how an atom trap works.

Now I think the evaporative cooling stage does work more like what you described -- a strong magnetic field acting on the atoms' magnetic moments -- but we don't do evaporative cooling, so I'm not so clear on the details.

This was a simply fabulous piece of writing, and a stunning blog! If this is a sample of what all the archives would contain in the future, I'm afraid that I won't be able to do anything more in Life (not that I was going to anyway) except to sort of "leech" here for the rest of it (whatever li'l remains) ... And I'll still have NO regrets!

Incredibly delightful. I really enjoyed it. Please keep it up.
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>Eric Cornell and Carl Wieman created the first BEC,
>using a combination of laser and magnetic cooling
>equipment.

And I'll be a little picky about the above.... Although this is certainly how these results have been sold a lot of the time, it really isn't true. He4 if you get it cold enough goes superfluid and becomes a Bose condensate. This was first demonstrated by Kapitsa and coworkers in the late 30s, but probably had been generated earlier. Cornell and Weiman were the first make a condensate out of dilute Bose gases, which for various reasons is a kinda more ideal case of a Bose condensate, but superfluid He4 still counts.

Cornell, Weiman, and Ketterle got the Nobel prize "for the achievement of Bose-Einstein condensation in dilute gases of alkali atoms, and for early fundamental studies of the properties of the condensates". Notice the qualifier.

Great piece of writing, thank you Jennifer; had never heard of the Kaye or Efimov effects. And thaks to Mary and P. Armitage for the clarifications.
And that is a nice pix of Fergie!

Looking for distributed proof reading?

figured out to keep the effect

suggest:

figured out how to keep the effect

So, Lou Gehrig goes to his doctor. His doctor says, "I have bad news. You've got Lou Gehrig's Disease." Lou says, "I really should have seen that coming".

I'm shocked, i say Shocked, that the Borromean ring wasn't discovered by someone named Borromean, or Ring or something.

Was recently introduced to this blog. Love it. But in last week, have come across a couple of other triskelion symbols and photos and information on triskelion. For symbol information, I recommend: http://www.symbols.com/encyclopedia/32/index.html, which is suggestive of a number of other traditional symbols for Efimov effect. And, then, on back cover of New Yorker [04/16/07], I spotted this photo for ad for Travel Channel's 1000 Places. It's the photo of surfer jumping into water at Ipanema Beach, Brazil.

Well, I don't seem to have figured out how to copy the picture I scanned and saved for web into this blog. Is it possible to do so? Or is this something discouraged here?

Lisbeth Jardine
Port Angeles, WA


Hi Lisbeth -- I don't actively discourage anything except trolls in the comment section, so the trouble you're having with pix might be a feature of the Typepad hosting service... I'm not adept at some of the more advanced features. :)

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    Physics Cocktails

    • Heavy G
      The perfect pick-me-up when gravity gets you down.
      2 oz Tequila
      2 oz Triple sec
      2 oz Rose's sweetened lime juice
      7-Up or Sprite
      Mix tequila, triple sec and lime juice in a shaker and pour into a margarita glass. (Salted rim and ice are optional.) Top off with 7-Up/Sprite and let the weight of the world lift off your shoulders.
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      The perfect nightcap after a long day struggling with QED equations.
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      1/2 oz light rum
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      2 oz light cream
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      In a shaker half-filled with ice, combine the dark and light rum, Tia Maria, and cream. Shake well. Strain into an old fashioned glass almost filled with crushed ice. Dust with the nutmeg, and serve. Bongos optional.
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      Electrify your friends with amazing pyrotechnics!
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      Combine Campari and lemon juice in shaker filled with cracked ice. Shake and strain into chilled cocktail glass. Heat brandy in chafing dish, then ignite and pour into glass. Cocktail Go BOOM! Plus, Fire = Pretty!
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      3/4 Triple sec
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