Research Highlights

Most known extrasolar planetary systems comprise planets whose orbits vary wildly from the nearly circular ellipses found in our solar system. This wide variation in eccentricity is thought to occur when large gas planets interact with each other, causing gyrations in planetary orbits, planet migrations toward and away from the central star, and even the ejections of planets out of the star system. 

The Anderson and Cornell groups have adapted two statistical techniques used in astronomical data processing to the analysis of images of ultracold atom gases. Image analysis is necessary for obtaining quantitative information about the behavior of an ultracold gas under different experimental conditions. 

According to the laws of quantum mechanics, identical fermions at very low temperatures can’t collide. These unfriendly subatomic particles, atoms, or molecules simply will not share the same piece of real estate with an identical twin. A few years back, researchers in the Ye lab considered this unneighborly behavior a big advantage in designing a new optical atomic clock based on an ensemble of identical ⁸⁷Sr atoms. 

A while back, former graduate student Scott Papp, graduate student Juan Pino, and Fellow Carl Wieman decided to see what would happen as they changed the magnetic field around a mixture of two different rubidium (Rb) isotopes during Bose-Einstein condensation.

The new molecules are as big as a virus. They’re ultracold. And, they’re held together by a ghostly quantum mechanical force field with the energy of about 100 billionths of an electron volt. These strange diatomic rubidium (Rb) molecules are the world’s first long-range Rydberg molecules. They were recently formed in Tilman Pfau’s laboratory at the University of Stuttgart from an ultracold cloud of Rb atoms. 

The most peculiar and fragile "molecules" ever discovered are the weakly bound triatomic Efimov molecules that form under specific conditions in a Bose-Einstein condensate (BEC). JILA theorists have now shown that such molecules can interact with an additional atom to form "daughter" molecules, which inherit many of their mother’s characteristics.

Our solar system is currently sprinting around the center of the Milky Way at a speed of 26 km/sec. But, we’re not just hurtling through empty space, according to Fellow Jeff Linsky and former graduate student Seth Redfield (now assistant professor of astronomy at Wesleyan University). We’re surrounded by 15 "nearby" clouds of warm gas, all within 50 light years of the Sun. Three of the nearest ones are shown in the figure. 

Supermassive black holes inside blazar galaxies emit powerful jets of particles traveling in opposite directions near the speed of light. Some are aimed toward the Earth. These jets emit radio waves, which makes them visible to radio telescopes as they streak across the sky. By studying these radio waves, scientists have determined that the jets are traveling at about 99.5% the speed of light and thus exhibit the effects of relativity. The blazars themselves are unusually variable, and many emit ultrahigh-energy γ-rays.

Monodromy literally means "once around." The term is applied in mathematics to systems that run around a singularity. In these systems, a parameter that describes the state of the system changes when the system loops around the singularity. Since monodromy’s discovery in 1980, mathematicians have predicted that many physical systems have it, including pendulums and tops as well as atoms and molecules.

The Weber group wants to understand how the individual building blocks of DNA interact with ultraviolet (UV) light. Such knowledge would be an important step toward gaining a detailed understanding of the molecular processes responsible for the UV-induced DNA damage that results in mutations and can lead to cancer or cell death.

Our comfortably middle-aged Sun completes a rotation once every 28 days. In contrast, young Sun-like stars spin much faster, sometimes whipping around 10 times as quickly. According to widely accepted theory, these young suns build magnetic fields in their convection zones by dynamo processes. Observations of these stars indicate strong magnetic activity.

In the summer of 2008, Fellow Jun Ye spent a couple of months at CalTech, where he ran into another visiting professor, former JILA Fellow Peter Zoller. Zoller left JILA in 1994 to become Professor of Physics at the University of Innsbruck (Austria). Besides riding bikes together in the mountains, the two men engaged in happy and fruitful discussions about Ye’s work developing a strontium- (Sr-) based optical atomic clock and Zoller’s pioneering research on quantum computing. It took them a matter of a couple of weeks to come up with a basic theoretical framework for a quantum computer based on alkaline-earth metals such as Sr.

Starting with ultracold atoms in a Bose-Einstein condensate, it’s possible to create coherent superpositions of atoms and molecules. Fellow Carl Wieman and others have done exactly this. Recently, the Jin group wondered if it would be possible to accomplish the same thing starting with a normal gas cloud of atoms.

Quantum dots are tiny structures made of semiconductor materials. With diameters of 1–5 nm, they are small enough to constrain their constituents in all three dimensions. This constraint means that when a photon of light knocks an electron into the conduction band and creates an electron/hole pair, the pair can’t get out of the dot.

Understanding how molecules collide is a hot topic in ultracold physics. Knowing the number of times molecules crash into each other and what happens when they do helps theorists predict the best ways to cool molecules to merely cold (1 K–1 mK), pretty cold (1 mK–1 µk), or ultracold (< 1 µK) temperatures.

The most important step for a microscope wanting to marry another microscope is finding the right partner. A professional matchmaker, such as the Perkins lab, might be just the ticket. The group recently presided over the nuptials of atomic force microscopy and optical-trapping microscopy. Research associate Gavin King, graduate students Ashley Carter and Allison Churnside, CU freshman Louisa Eberle, and Fellow Tom Perkins officiated. The marriage produced an ultrastable atomic force microscope (AFM) capable of precisely studying proteins in real-world (ambient) conditions.

Fellows Steve Cundiff and Ralph Jimenez have created two precision optics instruments with a priceless potential for shedding light on condensed-matter and biological physics. Instrument shop staffer Kim Hagen aided and abetted them in their endeavor by creating exquisite CAD drawings and machining precision parts.

To be the best they can be, optical atomic clocks need better clock lasers — lasers that remain phase coherent a hundred times longer than the very best conventional lasers. For instance, light from the clock laser in Fellow Jun Ye’s lab can travel around the Earth 10 times before it loses coherence. However, realizing the potential of the lab’s optical clock requires that the laser light remain coherent for 1000 trips around the Earth. The brute force solution to this problem would be to operate the clock laser at 4 K. This approach would increase the cost, complexity, and size of the optical clock as well as rendering it impractical for space exploration and travel.

Solvents — those things like water that dissolve other things like salt or sugar — are key players in some chemical reactions. That’s why the Lineberger group has come up with a nifty, but simplified, model system for studying solvent behavior. The group investigates the photodissociation and recombination of simple gas-phase anions, such as iodine bromide (IBr^-), when they are surrounded by different numbers of carbon dioxide (CO₂) solvent molecules.

The Greene group just figured out everything you theoretically might want to know about four fermions "crashing" into each other at low energies. Low energies in this context mean ultracold temperatures under conditions where large, floppy Feshbach molecules form. The group decided to investigate four fermions because this number makes up the smallest ultracold few-body system exhibiting behaviors characteristic of the transition between Bose-Einstein condensation and superfluidity.