World's coolest molecules

Aug 21, 2014
An optical cavity was used to control the wavelength of some of the lasers used for the magneto-optical trap. Credit: Michael Helfenbein

It's official. Yale physicists have chilled the world's coolest molecules.

The tiny titans in question are bits of strontium monofluoride, dropped to 2.5 thousandths of a degree above absolute zero through a laser cooling and isolating process called magneto-optical trapping (MOT). They are the coldest molecules ever achieved through direct cooling, and they represent a physics milestone likely to prompt new research in areas ranging from quantum chemistry to tests of the most basic theories in .

"We can start studying chemical reactions that are happening at very near to absolute zero," said Dave DeMille, a Yale physics professor and principal investigator. "We have a chance to learn about fundamental chemical mechanisms."

The research is published this week in the journal Nature.

Magneto-optical trapping has become ubiquitous among atomic physicists in the past generation—but only at the single-atom level. The technology uses lasers to simultaneously cool particles and hold them in place. "Imagine having a shallow bowl with a little molasses in it," DeMille explained. "If you roll some balls into the bowl, they will slow down and accumulate at the bottom. For our experiment, the molecules are like the balls and the bowl with molasses is created via laser beams and magnetic fields."

Until now, the complicated vibrations and rotations of molecules proved too difficult for such trapping. The Yale team's unique approach drew inspiration from a relatively obscure, 1990s research paper that described MOT-type results in a situation where the usual cooling and trapping conditions were not met.

DeMille and his colleagues built their own apparatus in a basement lab. It is an elaborate, multi-level tangle of wires, computers, electrical components, tabletop mirrors, and a cryogenic refrigeration unit. The process uses a dozen lasers, each with a wavelength controlled to the ninth decimal point.

"If you wanted to put a picture of something high-tech in the dictionary, this is what it might look like," DeMille said. "It's deeply orderly, but with a bit of chaos."

It works this way: Pulses of strontium monofluoride (SrF) shoot out from a cryogenic chamber to form a beam of molecules, which is slowed by pushing on it with a laser. "It's like trying to slow down a bowling ball with ping pong balls," DeMille explained. "You have to do it fast and do it a lot of times." The slowed molecules enter a specially-shaped magnetic field, where opposing pass through the center of the field, along three perpendicular axes. This is where the molecules become trapped.

"Quantum mechanics allows us to both cool things down and apply force that leaves the levitating in an almost perfect vacuum," DeMille said.

The Yale team chose SrF for its structural simplicity—it has effectively just one electron that orbits around the entire molecule. "We thought it would be best to start applying this technique with a simple diatomic molecule," DeMille said.

The discovery opens the door for further experimentation into everything from precision measurement and quantum simulation to ultracold chemistry and tests of the standard model of particle physics.

Explore further: Measuring electrons: Precise computations of their shape support Standard Model of physics

More information: Magneto-optical trapping of a diatomic molecule, Nature 512, 286–289 (21 August 2014) DOI: 10.1038/nature13634

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User comments : 4

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Egleton
1 / 5 (4) Aug 21, 2014
From this we can deduce that anthropogenic global warming is a hoax. We have found one very cold molecule.
Toiea
2.3 / 5 (3) Aug 21, 2014
We haven't found it, we prepared it anthropogenically.
mikep608
1 / 5 (1) Aug 23, 2014
They can make very dense objects from molecules this cold. Also the necleus should be very stable. they should try this with uranium and see if it's as radioactive. They should test to see if the amount of force needed to cool it to this same temperature is proportional to the wight of the nucleus. They should also see if atoms this cold can emit EMR, and also see if electricity flows faster/ the necleus can have faster or slower electron orbiting speed based on the temperature. the kinetic energy should be going somewhere though.
mikep608
1 / 5 (1) Aug 23, 2014
. the kinetic energy should be going somewhere though.


Actually, the kinetic energy might not need to be displaced onto something else. (law of conservation of energy) Why? Because this is where the mechanism for the measurement of energy begins and ends.We now enter into the world of what mysterious material that a proton is made from.The law of conservation of energy no longer applies........

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