Research Highlights

When will the Laser Interferometer Space Antenna (LISA) fly? Fellows Jim Faller and Peter Bender first proposed the basic concept behind LISA more than 25 years ago. The joint European Space Agency/NASA mission first scheduled a possible launch in 2012. The date has now slipped to 2017, with additional delays possible. Both agencies are grappling with limited budgets and conflicting priorities. In the United States, plans for a future manned spaceflight to Mars are competing for funding with basic science-oriented space programs like LISA.

The breakdown of chlorofluorocarbons (CFCs) in the stratosphere has been implicated in the destruction of Earth's protective ozone layer. Consequently, scientists have undertaken studies to better understand the structure and behavior of highly reactive, but short-lived, free radicals produced during the breakdown process. The molecules, which contain either fluorine or chlorine, are an important source of atmospheric halogen atoms. Elucidating their 3D structure and dynamical behavior will help scientists better understand atmospheric chemistry as well as their fundamental molecular properties.

A solvent is something that dissolves or disperses something else. It's the water in salt water, the alcohol in cough syrup, the lactates or ethers in inks. For many of us, solvents are the background music of the chemistry taking place all around us. But this isn't how Fellow Carl Lineberger and his colleagues in chemical physics think about solvents. Lineberger, Former Research Associate Vladimir Dribinski, Graduate Students Jack Barbera and Josh Martin, and student visitor Annette Svendsen see them as key players in some chemical reactions, right down to the level of quantum mechanical interactions.

"In the right light, in the right time, everything is extraordinary," according to photographer Aaron Rose. He could have just as easily been describing precision optical spectroscopy experiments recently conducted by Research Associates Tanya Zelevinsky and Tetsuya Ido, Graduate Students Martin Boyd and Andrew Ludlow, Fellow Jun Ye and collaborators from Poland's Instytut Fizyki and NIST's Atomic Physics Division.

Life can be challenging on the biophysics research frontier. Consider gold nanoparticles as a research tool, for example. Gold is ductile and malleable as well as being a good conductor of heat and electricity. Its unique chemistry allows proteins and DNA to be easily attached to these nanoparticles. Physicists have been investigating gold nanoparticles in optical-trapping experiments because they enhance trapping efficiency and potentially increase detection sensitivity.

The fine structure constant is getting a lot of attention these days. Known as α, it is the "coupling constant," or measure of the strength of the electromagnetic force that governs how electrons, muons, and light interact. What's intriguing is that new models for the basic structure of matter predict that α may have changed over vast spans of cosmic time, with the largest variations occurring in the early universe. However, the Standard Model says a has always been the same. Our basic understanding of physics depends on scientists' ability to determine whether or not α is an "inconstant constant."

There's only one way to prove you've invented a better atomic clock: Come out on top of a comparison of your clock with one of the world's best atomic clocks: The NIST-F1 cesium fountain atomic clock, the nation's primary time and frequency standard. NIST-F1 is so accurate it won't gain or lose a second in more than 60 million years.

Galaxy clusters contain enormous clouds of gas whose cooling should result in the formation of a multitude of new stars. But that's not what NASA's Chandra X-ray Observatory is detecting. Instead there's a whole lot less gas cooling and new star formation than scientists had predicted. Perhaps the most mysterious discovery of all is that the clusters are humming – a low B-flat 57 octaves below middle C. The hum originates from ripples of sound waves washing through great galactic gas clouds surrounding supermassive black holes.

Imagine trying to describe the intricate motions of a single atom as it interacts with a laser. Then suppose you could generalize this understanding to a whole cloud of similar atoms and predict the temperatures your experimental physicist colleagues could achieve with laser cooling. This way-cool theoretical analysis comes compliments of Graduate Student Josh Dunn and Fellow Chris Greene.

Juri Toomre and his group concentrate their stellar research close to home--just 93 million miles away, to be precise. They want to answer the question: What dynamic processes occur deep within the Sun? To find out, they use a powerful combination of computer simulations and helioseismology (which analyzes sound waves produced by the Sun to probe its internal structure.) The researchers believe that working out the details of the Sun's internal structure should lead to explanations for the 22-year sunspot cycle and other regular surface features such as the Sun's consistent, but variable, rotation rate.

Our lives depend on heme. As part of hemoglobin, it carries oxygen to our tissues. As part of cytochrome c, it helps transform the energy in food into the energy-rich molecule ATP (adenosine triphosphate) that powers biochemical reactions that keep us alive and moving. As part of cytochrome P450, it helps break down toxic chemicals in our bodies.

Science sleuths have a new and powerful method for identifying (and investigating) atoms and molecules, thanks to Graduate Student Mike Thorpe, Research Associate Kevin Moll, Senior Research Associate Jason Jones, Undergraduate Student Assistant Ben Safdi, and Fellow Jun Ye. The new method allows them to study molecular vibrations, rotations, and collisions as well as temperature changes and chemical reactions.

Gamma-ray bursts signal the birth of a new black hole, whether it's created during the collapse of a massive star or via a merger between two compact objects such as neutron stars. Astrophysicists have determined that long gamma-ray bursts are associated with collapsing stars and short bursts are associated with binary mergers. In both cases, however, black-hole accretion powers the burst. 

One fun thing theorists do is undertake creative projects that predict phenomena that haven't yet been observed experimentally. In fact, sometimes they even predict things no one has ever imagined before. In other cases, the goal is to unravel the mechanism behind an experimental result that initially seems to conflict with the known laws of quantum physics. Fellow Chris Greene's group enjoys self-driven, innovative work in both categories.

Black holes are pretty strange, sucking in not only nearby matter but also the space around it. These cosmic vacuum cleaners are powered by thin, gaseous accretion disks in orbit around them. Something drives the orbiting gas to spiral in toward the black hole, where all trace of it disappears forever into the singularity. One of the exciting challenges in astrophysics is to figure out the physics driving this process, which keeps black holes growing for billions of years after they're formed.

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. 

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.

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.