Research Highlights

JILA physicists are collaborating to explore the link between superconductivity and Bose-Einstein condensation (BEC) of fermions at ultracold temperatures. Fermions have an odd number of total protons, neutrons, and electrons, giving them a half integer spin, which is either up or down. At ultracold temperatures, this means fermions can't just occupy the same energy level (like bosons, which have an even number of atomic constituents) and form one superatom in a BEC. Instead, they stack up in the lowest energy states, with two fermions in each state, one spin up and one spin down, forming a Fermi sea.

When molecules smash into each other, things happen on the quantum level. Electrons get shoved around. They may even jump from one atom to another. Spin directions can change. A chemical reaction may even take place. Since it's not possible to directly observe this kind of electron behavior, scientists want to be able to probe it with novel spectroscopies. Now, thanks to a recent theoretical study, ultracold spectroscopy looks particularly promising for elucidating electron behavior during molecular impacts.

We know a lot about cool stars because our Sun is one of them. However, we can't know for sure if cool stars produce winds (like the Sun does) without looking for evidence of such winds. Where stellar winds exist, they interact with hydrogen in the interstellar medium far from the star to produce tell-tale absorption in stellar ultraviolet spectral lines. 

One way to understand unstable molecules is to systematically create slightly different versions of a similar stable molecule and investigate each new molecule with identical analysis and experiments. That is exactly what researchers from JILA and CU are doing with a series of ringed molecules.

Graduate Student Sarah Thompson, Research Associate Eleanor Hodby, and Fellow Carl Wieman have come up with a novel way to assemble Feshbach molecules from a cloud of ultracold atoms. The molecules consist of very weakly bound atoms that are about as far apart in the molecular state as they are in the atom cloud from which they are formed. Understanding the properties of these molecules promises to help researchers better understand Bose-Einstein condensation and ultracold fermionic systems.

High-energy radiation is notorious for damaging DNA, primarily by breaking chemical bonds. Damage to DNA can cause mutations, cancer, or even death. Much of this damage is inflicted by secondary, or low-energy, electrons knocked out of atoms in the DNA molecules by radiation. The low-energy electrons get captured by the DNA bases (which make up the letters of the genetic code), temporarily forming a negatively charged molecule (anion). The anion lasts just long enough to transfer its excess energy to the weakest nearby chemical bond, often breaking it.

Scientists believe that planetary systems coalesce from disks of gas and dust orbiting a star. Similarly, stars can form within massive accretion disks orbiting a black hole. Determining the mechanisms that create stars and planets from these orbiting disks is a hot topic among astrophysicists, according to JILA Fellow Phil Armitage and colleagues W. K. M. Rice of the University of California, Riverside, and G. Lodato of Cambridge's Institute of Astronomy.

When Albert Einstein said, "the only reason for time is so that everything doesn't happen at once," he didn't know about studies performed by Senior Research Associate Christine Hackman and Fellow Judah Levine. These time-and-frequency experts work quite hard to devise ways of comparing the accuracy and stability of the world's premier atomic clocks - so that things like satellite communications and high-tech navigation can happen precisely when they're supposed to, including all at once.

Chemical physicists investigate the structure and behavior of atoms and molecules on the quantum level. Such research is particularly challenging when the molecule under investigation appears in small amounts and is rapidly transformed into something else, e.g., during combustion, chemical synthesis, or atmospheric chemical reactions. Happily, Research Associate Feng Dong, Fellow David Nesbitt, and former JILAn Scott Davis (now with Vescent Photonics in Denver) have developed an innovative method for studying such elusive chemicals.

"Watch" atoms collide! Thrill to the twists and turns of potassium atom wave functions as the atoms come closer and closer to impact! "See" the atoms deform, then recover as they smash together and fly apart inside a dense atomic vapor! It's all in a day's work for Graduate Student Virginia (Gina) Lorenz and Fellow Steve Cundiff.

Scientists in Fellow Jun Ye's lab are developing a high-precision optical atomic clock linked to super-narrow optical transitions in ultracold, trapped strontium atoms. However, unless the new clock is portable (it is not) or researchers figure out how to accurately transmit its clock signal over a fiber optic network to NIST, the legendary strontium clock will not be able to help the world keep better time.

Giant gas planets don't often stay in orbit where they're formed. They often move closer to their star or, occasionally, further away. Seldom do they remain in almost circular orbits such as those of Jupiter and Saturn. In fact, all but one of the giant gas planets discovered around other stars are closer to their star than Jupiter is to the Sun. A fraction of these planets are even closer than Mercury!

For nearly 18 years, JILA Fellow Dick McCray has been studying the brightest supernova to light up Earth's night skies since the Renaissance. Known as 1987A because it appeared in the southern sky on February 23, 1987, the supernova occurred when a 10-million-year-old blue supergiant star exploded in the Large Magellanic Cloud, a galaxy located 160,000 light years from Earth.

Understanding dark matter's role in the distribution of galaxies in the Universe is a central question in cosmology. Dark matter pervades the universe. Haloes of dark matter surround galaxies and galaxy clusters. Dark matter also forms filamentary structures that connect these haloes, forming a cosmic web, as illustrated on the right. Until recently, cosmologists tried to understand the distribution of galaxies with theoretical analyses using different-sized dark matter haloes containing zero, one, or more galaxies.

Brad Perkins and his thesis advisor Fellow David Nesbitt recently decided to explore what happens when fast, cold carbon dioxide molecules collide with the surface of an oily liquid (perfluoropolyether). Of course, you can only do these sorts of things in a vacuum chamber, where there are virtually no other gas molecules in the air to get in the way! The vacuum chamber itself creates an additional challenge: working with liquids at very low pressures.

Gamma-ray jets produced deep within massive stars can blow apart the star when they emerge, creating a supernova. The jets are very light and travel near the speed of light toward the star's surface. They are created by a complex interaction of a black hole, an accretion disk, and very strong magnetic fields that come into being when a massive star depletes its supply of hydrogen fuel and falls into itself.

Graduate students Dave Harber and John Obrecht, postdoc Jeff McGuirk, and Fellow Eric Cornell recently devised a clever way to use a Bose-Einstein condensate (BEC) inside a magnetic trap to probe the quantum behavior of free space. To do this, the researchers first created a BEC inside a magnetic trap, whose shape (where the condensate forms) resembles a cereal bowl. Then as shown in the diagram to the right, they moved the BEC in the bowl closer and closer to a glass surface until distortions in the shape of the bowl appeared.

RNA molecules can perform amazing biological feats, including storing, transporting, and reading genetic blueprints as well as catalyzing chemical reactions inside living cells. To manage the latter feat, RNA molecules must rapidly fold into an exact three-dimensional (3D) shape. Understanding how RNA accomplishes this is a major scientific challenge. Former JILA postdoc Jose Hodak, Christopher Downey (doctoral candidate in Chemistry and Biochemistry), JILA graduate student Julie Fiore, Chemistry and Biochemistry Professor Arthur Pardi and Fellow David Nesbitt are meeting this challenge head on.

The race is on! Two mice chase one another around a curvy, roughly elliptical white stripe. But, the goal can't be the finish line – because there isn't one. Rather, the contest seems to be: Which mouse will stay on track for the longest time before spinning out of control? Of the two, one clearly "wags its tail" less as its phototransistor eyes guide it along the reflective white strip. 

Fellow Jan Hall has been working on stabilizing the frequency of lasers since the 1960s. Now, he, JILA Research Associate Mark Notcutt, Long-Sheng Ma (currently at BIPM in France), and Fellow Jun Ye have devised an improved, compact, and less expensive method for stabilizing lasers. The new method is based on a small, vertically mounted optical cavity (shown on the right). Because the cavity is supported exactly in the middle, the top and bottom halves change in length by equal and opposite amounts in response to vibrations.