Research Highlights

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.

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.

Senior research associate Brad Hindman of the Toomre group uses helioseismology to understand what’s happening under the surface of the Sun. Helioseismology is a lot like the ultrasound tests used to evaluate medical conditions. However, there’s a big difference: physicians already have a good idea of the basic structures they are probing with sound waves. Helioseismologists don’t. They study sound that travels below the Sun’s surface to learn about the structure and behavior of the Sun’s convection zone, which comprises the outer third of the Sun. However, if they misinterpret the nature of the sounds they analyze, then they are likely to miss the mark in determining what’s happening inside the Sun.

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.

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.

A faint star that can easily be seen from Earth with binoculars has a Jupiter-like gas planet orbiting it once in just three days. That means the planet is close enough to its Sun-like star to get scorching hot, which affects both the planet and its atmosphere. The star is called HD209458, and its planet’s moniker is HD209458b.

A while back, Fellow Eric Cornell started thinking about all the waste heat produced by the use of water to cool refi neries and other industrial plants. In a few places, the waste hot water — at ~212°F — is used to heat commercial and apartment buildings. 

When former graduate student Mingming Feng started his thesis project, his goal was to build and characterize a mode-locked quantum dot diode laser in Kevin Silverman’s lab at the National Institute of Standards and Technology (NIST).

If you want to understand how chemical reactions happen, the ability to monitor dynamic positions of atoms in a molecule is critical. There's a well-known laser technique known as coherent Raman spectroscopy that uses a scattering laser pulse to set atoms vibrating and then measures the color shift of reflected light to detect vibration patterns. This technique has been used as a molecular fingerprinting device for simple motions of a molecule.

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.

Fellow Phil Armitage and colleagues from the Université de Bordeaux and Google, Inc. are key players in the quest to understand the secrets of planet formation. Current theory posits that there are three zones of planet formation around a star (as shown in the figure). In Zone One, the hot innermost zone, small rocky planets form over a period of hundreds of millions of years. The planets form too slowly to accrete gas from the original planetary disk. Zone One is the terrestrial, or habitable, zone.

When Richard Sandberg and his colleagues in the Kapteyn/Murnane group developed a lensless x-ray microscope in 2007 (see JILA Light & Matter, Winter 2008), they were delighted with their ability to obtain a stick-figure image (below) that was comparable in resolution to one from a scanning-electron microscope. 

Imagine being able to observe how a magnet works at the nanoscale level, both in space and in time. For instance, how fast does a nanoscale magnetic material switch its orientation? What if understanding magnetic switching might lead to the use of the spin of an electron rather than its charge to create new devices? A new method for investigating such possibilities is just beginning to be explored.

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.

Fellow Phil Armitage studies the migration of gas giant planets through evolving protoplanetary disks. He and former JILA postdoc Richard Alexander (Universiteit Leiden) have designed relatively simple models that reproduce the observed frequency and distribution of extra-solar giant planets, many of which orbit very close to their stars. The models also replicate the masses, lifetimes, and evolution of protoplanetary disks.

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.

Carl Lineberger and his group recently achieved some exciting firsts: (1) the experimental observation of the oxyallyl diradical, a key intermediate in a series of important chemical reactions, and (2) the posting of an abstract of the Angewandte Chemie cover story reporting this achievement — on Facebook! While the Lineberger group is responsible for the clever design of the photoelectron spectroscopy experiments that led to the observation of oxyallyl diradical, Lineberger was astonished that his work got on Facebook. He speculated that the journal’s publisher, Wiley-VCH, was responsible.

Heat does not always flow as rapidly near nanostructures as it typically does in solids. Instead, it can go ballistic! Ballistic heat transfer occurs near a tiny device if its size is smaller than the distance a phonon, or lattice vibration, travels before colliding with another phonon. When this happens, heat flow is reduced, and a nanoscale hot spot is created. Ballistic heat transfer away from a hot spot can be as much as three times less efficient than ordinary heat diffusion.