Research Highlights

"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.

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!

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.

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.

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.

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.

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.

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.

Rosalba Perna and colleagues Jonathan Granot of Stanford and Enrico Ramirez-Ruiz of Princeton's Institute for Advanced Study recently figured out the relationship between X-ray flashes, X-ray rich gamma-ray bursts, and gamma-ray bursts detected by different space-based observatories. X-ray flashes are transient astronomical X-ray sources that last from several seconds to a few minutes. T

Lora Nugent-Glandorf and Tom Perkins have come up with an optical trap motion detector that can "see" protein motors moving one base at a time along a DNA helix. For some time scientists have been able to make optical traps that can track the movement of attached beads, but the method had a resolution of 1-2 nanometers, which was not sensitive enough to resolve .338 nm DNA base steps. The lack of resolution was mostly due to instrument drift.

What really happens inside black holes? Andrew Hamilton and Scott Pollack, a graduate student in the Physics Department, recently decided to investigate the answer to this question. In the process, they developed a model using realistic physics that they believe better describes the internal structure of black holes.

Jason Jones, Kevin Moll, Mike Thorpe, and Jun Ye have generated the world's first precise frequency comb in the extreme ultraviolet (EUV) using a combination of an ultrafast mode-locked laser and a precision high-finesse optical cavity. The EUV frequency comb consists of regularly spaced sharp lines that extend into the EUV region of the electromagnetic spectrum.

Andrew Hamilton and Jason Lisle, who received his Ph.D. in astrophysical and planetary sciences in 2004, have proposed a new model for the flow of matter into stationary and rotating black holes. In their "river model of black holes," space flows like a river through a flat background, while objects (like light rays) that move through the river abide by the rules of special relativity. 

A high-powered JILA collaboration led by JILA Fellows Jun Ye and Chris Greene is making important progress toward developing an ultrastable, high-accuracy optical atomic clock. The new optical clock design will use a variety of laser sources including a femtosecond comb and a diode laser stabilized with an optical cavity, which, in turn, is locked to a narrow energy level transition in ultracold strontium atoms.

Three years ago Jun Ye decided to apply an old idea for amplifying and stabilizing continuous-wave (cw) lasers to state-of-the-art ultrafast lasers. In 2002, Jason Jones, a postdoctoral fellow with Jun, analyzed whether the build-up cavities used to amplify cw laser outputs could be modified to work with ultrafast, mode-locked lasers. His detailed calculations suggested that it would be possible but technically demanding.

Imagine high-school or college students so excited about physics they can hardly wait to get to class every day and learn more about how the world works. Fellow Carl Wieman recently offered cogent suggestions to new physics teachers on coming closer to this ideal. First, he recommended starting with research on how people learn physics and paying particular attention to the concept of "cognitive load." This concept, which posits that people can only process about seven ideas in short-term working memory, sets clear limits on how much information can be effectively introduced in a single lesson (or scientific talk).

Pete Roos, Tara Fortier, Xiaoqin Li, Ryan Smith, Jessica Pipis, and Steve Cundiff are using a phase-controlled mode-locked laser to control quantum processes in semiconductors. Semiconductors are capable of producing electrical currents from light (and vice-versa) and are the basis for a wide variety of optoelectronic devices, including photodiodes, light-emitting diodes, and solar cells.