Physicists Operate Lasers To Tricks Molecules

Molecules are hot. They zip, spin and vibrate with frenetic motion. They jiggle and twist on the inside and bounce on the outside, imparting structure and physical properties to nearly everything that exists. Nevertheless by achieving temperatures colder than any in the natural world, physicists can almost stop these rush demons cold. Like surgeons who slow a beating heart by packing ice sorrounding a patient"s chest, physicists have recently coaxed molecules into ultracold states in which motion is nearly gone. Researchers are left with intriguing, exquisitely controllable fresh specimens to poke and prod, enabling experiments that would be impossible with everyday hot molecules that rotate and vibrate at their usual frenzied pace. To still these jittery molecules, temperatures must descend to about 350 nanokelvins, only a sliver above absolute zero and far colder still than the depths of outer period (about 3 kelvins, roughly 300 degrees Celsius colder than room te
mperature). Researchers have immediately figured elsewhere ways to reach such lows, using precise laser pulses to trick molecules into giving up energy in the form of light. As the temperature drops, energy is siphoned away from the molecules. These original experiments have created a large, stable supply of ultracold molecules stationary enough to operate on. "This is the breakthrough, " says Matthias Weidemüller, a physicist who was formerly at the University of Freiburg in Germany and whose class recently succeeded in making an ultracold lithium-cesium molecule. "The baggage that drives the whole field is to create ultracold systems that you can manipulate and observe." What motivates the scientists is the potential of ultracold molecules as modern tools for research. Such tools could relieve answer questions about the relationship between individual molecules as they collide: Cold chemical reactions are so slow that physicists have enough day to catch nuances of the
interactions between molecules. Researchers could harness lattices of trapped, frozen molecules to explore the application of quantum mechanics to data storage and transmission. And more fundamentally, ultracold molecules may enable physicists to discover new, exotic phases of matter, such as a kind of superfluid in which molecules act across extensive ranges to influence one another in a frictionless system. A virgin abundant supply of ultracold molecules has bumped physicists into their own excited state of high energy. "There is an awful group of detail and rich physics to explore, " says Paul Julienne, a theoretical physicist at the National Institute of Standards and Technology in Gaithersburg, Md. The jittery molecule Molecules, unlike the spherical atoms that compose them, are lumpy. Physicist Jun Ye says atoms are basketballs, and molecules American footballs. Two basketballs bounce off each other in a predictable way, says Ye, of the University of Colorad
o at Boulder. However molecules have awkward angles and unwieldy curves, making interactions less predictable. "Atoms are easier to control, " says Ye. "Molecules are more complex, and more exciting to study than atoms." Physicists have been able to freeze atoms using laser bright for years. On the other hand molecules-which come in a wide variety of shapes, sizes and charges-have proved to be a greater challenge. "The techniques to ultracool atoms can"t be used for molecules, " says Weidemüller, who is at the moment at Heidelberg University. "That"s why one had to come up with a beneficial trick to generate them slow." Physicists had identified two approaches for creating ultracold molecules: Hot molecules could be cooled, or already cold atoms could be cajoled into joining. Full text: http://computerandtechnologies.com/technology/news_2008-12-29-18-30-04-681.html