Direct laser cooling of molecules

Oct 21, 2010

Cooling molecules with lasers is harder than cooling individual atoms with lasers. The very process of laser cooling, in which atoms are buffeted by thousands of photons, was thought by many to be impossible for molecules since photons, instead of slowing and cooling the molecules, could actually excite internal motions such as rotations and vibrations. Consequently, to get cold molecules one method is to first cool atoms and then combine them into molecules.

Now Yale physicist David DeMille and his team have developed a way to cool directly with using three lasers instead of the two typically needed for atoms. By choosing the molecular species carefully --they experiment with SrF molecules-- and choosing the photon energies to avoid unwanted excitation of rotational motion, the cooling process can proceed.

In this way, molecular temperatures of 300 micro-K have been achieved, the lowest ever for direct cooling of molecules. This temperature pertains so far to motion along one selected dimension only, much as for the initial demonstrations of for atoms.

While these temperatures are less than a thousandth of a degree above absolute zero, they are for now orders of magnitude hotter than the cold molecules that can be made by first chilling individual atoms and then combining them. With the latter approach, however, the choice of molecules is presently limited to only those that can be made with alkali atoms. The SrF molecules used in the Yale experiment, by contrast, possess an unpaired electron. This makes them potentially useful as or in various studies of fundamental physics. In addition, the results from DeMille’s group indicate that laser cooling to yet lower temperatures is likely possible for SrF and other, similar molecules.

"The technique of laser cooling," says DeMille, "which has led to a revolution in atomic physics, has now been shown to also apply to (at least some) molecules. This significantly expands the range of molecules for which ultracold temperatures can be reached, which in turn opens a route to many new scientific applications."

David DeMille presents the findings at Frontiers in Optics (FiO) 2010/ Science XXVI -- the 94th annual meeting of the Optical Society (OSA).

Explore further: Acoustic tweezers manipulate cell-to-cell contact

add to favorites email to friend print save as pdf

Related Stories

Scientists using lasers to cool and control molecules

Sep 20, 2010

(PhysOrg.com) -- Ever since audiences heard Goldfinger utter the famous line, “No, Mr. Bond; I expect you to die,” as a laser beam inched its way toward James Bond and threatened to cut him in half, lasers ...

Using lasers to cool and manipulate molecules

Dec 07, 2009

(PhysOrg.com) -- "For years, we have been using laser cooling to trap and manipulate atoms," David DeMille tells PhysOrg.com. "This has been very useful for both basic science and many applications. Recent ...

Tailoring the optical dipole force for use on molecules

Oct 29, 2009

(PhysOrg.com) -- "Scientists have been working with dipole fields for quite some time," Peter Barker tells PhysOrg.com. "However, most of the work is focused on very small particles, like atoms, or on larger particles, such a ...

Scientists cool gas by laser bombardment

Sep 02, 2009

Three decades ago, American and Finnish scientists came up with a very powerful method for cooling gases by "laser bombardment." Only now were physicists at the University of Bonn able to demonstrate that it actually works. ...

Recommended for you

Acoustic tweezers manipulate cell-to-cell contact

8 minutes ago

Sound waves can precisely position groups of cells for study without the danger of changing or damaging the cells, according to a team of Penn State researchers who are using surface acoustic waves to manipulate ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Simonsez
not rated yet Oct 21, 2010
The laser: What CAN'T it do?

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.