News & Research Highlights

“Nature is built quantum mechanically,” says Fellow Jun Ye, who wants to understand the connections between atoms and molecules in complex systems such as liquids and solids (aka condensed matter). He says that the whole Universe is made of countless interacting particles, and it would be impossible to figure out the myriad connections between them one particle at a time, either theoretically or experimentally.

Graduate students or research associates at JILA have the option of signing up to help teach after-school science classes to elementary and middle school students in the St. Vrain School District. The volunteers expect to stimulate the children to learn to think critically, enjoy science activities, and become confident in their own abilities to master difficult concepts. What they may not anticipate at first is that they will learn some important skills themselves, including the ability to communicate scientific concepts in everyday language and, with that new ability, gain a better understanding of education.

The vision of a tabletop x-ray laser has taken a giant step into reality, thanks to Tenio Popmintchev, Ming-Chang Chen and their colleagues in the Kapteyn/Murnane group. By focusing a femtosecond laser into a gas, Popmintchev and Chen generated many colors of x-rays at once, in a band that stretched from the extreme ultraviolet into the soft x-ray region of the electromagnetic spectrum, spanning wavelengths of ranging from about 6 to 2.5 nm. This broad x-ray band has so many different colors that all the waves can be added together to form the shortest strobe light in existence.

The secret for reducing quantum noise in a precision measurement of spins in a collection of a million atoms is simple: Pre-measure the quantum noise, then subtract it out at the end of the precision measurement. The catch is not to do anything that detects and measures the spins of individual atoms in the ensemble. If states of individual atoms are measured, then those atoms stop being in a superposition and the subsequent precision measurement will be ruined.

Fellow Jun Ye’s group has enhanced the molecular fingerprinting technique with the development of a mid-infrared (mid-IR) frequency comb.  The new rapid-detection technique can now identify traces of a wider variety of molecules found in mixtures of gases. It offers many advantages for chemical analysis of the atmosphere, climate science studies, and the detection of suspicious substances.

Atomic force microscopy (AFM) just got a whole lot more efficient for studying proteins and other biomolecules. Graduate student Allison Churnside, former research associate Gavin King, and Fellow Tom Perkins recently used a laser to detect the position of sparsely distributed biomolecules on a glass cover slip. Since the same laser is also used to locate the AFM tip, it is now possible to align the microscope tip and sample with a precision of 40 nm, before the AFM tip even touches the sample. The researchers say that the new sample detection scheme solves the “needle in a haystack” problem of nanoscale microscopy.

Solvents don’t just dissolve other chemicals (called solutes) and then sit around with their hands in their pockets. Instead, they get involved in all sorts of different ways when dissolved molecules toss electrons around, i.e., they facilitate charge transfer events. In research, the hard part is fi guring out exactly how and when solvent molecules get involved when an electron hops from one solute molecule to another. For example, in liquids (which do most of the dissolving), solvent molecules move constantly, making it very challenging to see what they’re doing when charge transfer events occur.

In microscopic studies of single biological molecules or nanoparticles, it’s useful to be able to precisely control the temperature around the sample. Until now, heating has required electric currents that warm up microscope stages, slides, and optics in addition to the specimen under study. Such methods are slow and hard to control, not to mention capable of accidentally altering the chemistry or structure of the sample. Now there is a better solution for keeping samples nice and warm: The nanobathtub.

In 2008, the Deborah Jin Group introduced a new technique, known as atom photoemission spectroscopy, to study a strongly interacting ultracold gas cloud of potassium (40K) atoms at the crossover point between Bose-Einstein condensation and superfl uidity via the pairing of fermionic atoms (See JILA Light & Matter, Summer 2008). Near the crossover point, the physics of superfl uidity in an atom gas system may be connected to that of high-temperature superconductivity.

The Bohn group has just come up with an exciting, really complicated experiment for someone else to do. This is something theorists like graduate student Ryan Wilson, former research associate Shai Ronen, and Fellow John Bohn get a kick out of. In this case, they’re recommending an experiment to measure how fast a tiny blue laser would have to move through a dipolar Bose-Einstein condensate (BEC) to create ripples.

Fellows Deborah Jin, Jun Ye, and John Bohn are exploring new scientific territory in cold-molecule chemistry. Experimentalists Jin and Ye and their colleagues can now manipulate, observe, and control ultralow-temperature potassium-rubidium (KRb) molecules in their lowest quantum-mechanical state. Theorist Bohn analyzes what the experimentalists see and predicts molecule behaviors under different conditions.

The cold-molecule collaboration has developed a method for directly imaging ultracold ground-state KRb molecules. Their old method required the transfer of ultracold KRb molecules into a Feshbach state, which is sensitive to electric and magnetic fields. Thus researchers had to turn off the electric field and keep the magnetic field at a fixed value during the imaging process.

Mathias Weber and his team recently did the following experiment: They excited the methyl group (CH₃) on one end of nitromethane anion (CH₃NO₂^-) with an infrared (IR) laser. The laser got the methyl group vibrating with enough energy to get the nitro group (NO₂) at the other end of the molecule wagging hard enough to spit out its extra electron.

The Dana Z. Anderson group has developed a microchip-based system that not only rapidly produces Bose-Einstein condensates (BECs), but also is compact and transportable. The complete working system easily fits on an average-sized rolling cart. This technology opens the door to using ultracold matter in gravity sensors, atomic clocks, inertial sensors, as well as in electric- and magnetic-field sensing. Research associate Dan Farkas demonstrated the new system at the American Physical Society’s March 2010 meeting, held in Portland, Oregon, March 15–19, 2010.

Not content with stepping on their bathroom scales each morning to watch the arrow spin round to find their weights, former research associate John Teufel and Fellow Konrad Lehnert decided to build a nifty system that could measure more diminutive forces of half an attoNewton (0.5 x 10^-18 N). Their new system consists of a tiny oscillating mechanical wire embedded in a microwave cavity with an integrated microwave interferometer, two amplifiers (one of them virtually noiseless), and a signal detector.

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.

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.