Research Highlights

The Cosmic Origins Spectrograph, or COS, is a powerful new instrument scanning the Universe. COS was installed on the Hubble Space Telescope in 2009. Since then, it has been searching for clues about the composition of the Universe, including how galaxies like our own Milky Way formed and evolved over time. It is seeing beautiful things never before detected in the Universe because it is the lowest-noise ultraviolet (UV) spectrograph ever built for space exploration.

The dance of electrons as a bromine molecule (Br₂) separates into two atoms is intricate and complex. The process of breaking up takes far longer than expected (~150 vs 85 fs) because the cloud of electrons that bind atoms together in a molecule behaves as if it were still surrounding a molecule until the last possible moment — when the atomic fragments are about twice the normal distance apart (~.55 nm). At this point, there’s simply not enough energy left in the system to hold the molecule together. When the two atoms finally appear as separate entities, it was if someone had snapped a rubber band.

In 2008, the Ye and Jin groups succeeded in making ultracold potassium-rubidium (KRb) molecules in their ground state (See “Redefining Chemistry at JILA” in the Spring 2010 issue of JILA Light & Matter). Their next goal was to figure out how to precisely control chemical reactions of these ultracold polar molecules by manipulating the quantum states of the reactants. But first the researchers had to discover how to calm those reactions down enough to study them. Under the conditions in which they were made (an optical trap allowing motion in all three dimensions), ultracold KRb molecules were so chemically reactive they disappeared almost as soon as they were formed.

Putting the brakes on a superfluid dipolar Bose-Einstein condensate (BEC) just got a whole lot more interesting. Last year, the Bohn theory group explored what would occur in a dipolar BEC when a laser probe — think of it like a finger — tickled a BEC just hard enough to excite a roton.

In 2008-2009, much to their amazement,researchers working on the Jun Ye group’s neutral Sr optical atomic clock discovered tiny frequency shifts caused by colliding fermions! They figured out that the clock laser was interacting slightly differently with the Sr atoms inside a one-dimensional (pancake-shaped) trap. The light-atom interactions resulted in the atoms no longer being identical. And, once they were distinguishable, formerly unneighborly atoms were able to run into each other, compromising clock performance.

Hot Jupiters — giant gas planets orbiting close to their parent stars — aren’t just scorched (at temperatures of >1000 K). They are also swollen up larger than can be explained by the intense heat from their host stars. Recently Fellow Rosalba Perna and her colleagues from Columbia University and the Kavli Institute for Theoretical Physics suggested a reason why these planets are so puffed up: The swelling results from heat dissipated from electric currents generated by the interaction of robust magnetic fields (generated from deep within the giant planets) with strong atmospheric winds carrying charged particles called ions.

“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.

After he retired, Fellow Alan Gallagher decided to take his interest in solar energy in a whole new direction: He decided to design, build, and test a unique large-area frying pan heated by the Sun’s energy. The new solar frying pan was specifically tailored to the cooking of injera bread in East Africa.For more than 100 million people in East Africa, the thin, flexible, and pancakelike bread is a mainstay of their diet. It is usually eaten with a variety of thick sauces spread around the top of a large (~0.4 m diameter) slice, which serves as a shared “dinner plate.” 

There are two competing ideas about the origin of the monster black holes at the center of galaxies. Both include exceptional stars that have never actually been observed: (1) massive population III (Pop III) stars (as big as a thousand Suns) made of pure hydrogen and helium that would have formed less than 100 million years after the Big Bang, and (2) gigantic quasistars whose shining envelopes were powered, not by nuclear fusion, but by energy emitted by the black holes inside them.

Plucking the two electrons out of helium atoms should allow researchers to study how they interact during a double ionization process — at least in theory. Recently, Fellow Andreas Becker explored whether an ultrashort vacuum ultraviolet (VUV) laser pulse could be used to probe the interactions of helium’s electrons during a double ionization in the presence of an intense infrared (IR) laser field.

Of all the fundamental forces, gravity is the most difficult to precisely measure. This difficulty is reflected in how hard it is to accurately measure “Big G,” a fundamental constant that is part of the measurement of the gravitational force. In fact, big G is the least precisely measured fundamental constant in physics. Who would have imagined that the very first fundamental force to be discovered would still be somewhat mysterious more than 300 years later? Or, that a force most of us take for granted in everyday life is actually very hard to precisely measure?

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.

Before there were galaxies with black holes in their centers, there were vast reservoirs of dark matter coupled to ordinary matter, mostly hydrogen gas. These reservoirs were sprinkled with the Universe’s early stars born in pregalactic dark matter halos. But according to Fellow Mitch Begelman, another population of atypical stars formed millions of years later during the creation of galaxies. These stars grew to truly colossal sizes — a million times more massive than the Sun.

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.

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.