Research Highlights

Quantum dots are tiny structures made of semiconductor materials. With diameters of 1–5 nm, they are small enough to constrain their constituents in all three dimensions. This constraint means that when a photon of light knocks an electron into the conduction band and creates an electron/hole pair, the pair can’t get out of the dot.

Understanding how molecules collide is a hot topic in ultracold physics. Knowing the number of times molecules crash into each other and what happens when they do helps theorists predict the best ways to cool molecules to merely cold (1 K–1 mK), pretty cold (1 mK–1 µk), or ultracold (< 1 µK) temperatures.

Fellows Steve Cundiff and Ralph Jimenez have created two precision optics instruments with a priceless potential for shedding light on condensed-matter and biological physics. Instrument shop staffer Kim Hagen aided and abetted them in their endeavor by creating exquisite CAD drawings and machining precision parts.

The most important step for a microscope wanting to marry another microscope is finding the right partner. A professional matchmaker, such as the Perkins lab, might be just the ticket. The group recently presided over the nuptials of atomic force microscopy and optical-trapping microscopy. Research associate Gavin King, graduate students Ashley Carter and Allison Churnside, CU freshman Louisa Eberle, and Fellow Tom Perkins officiated. The marriage produced an ultrastable atomic force microscope (AFM) capable of precisely studying proteins in real-world (ambient) conditions.

Solvents — those things like water that dissolve other things like salt or sugar — are key players in some chemical reactions. That’s why the Lineberger group has come up with a nifty, but simplified, model system for studying solvent behavior. The group investigates the photodissociation and recombination of simple gas-phase anions, such as iodine bromide (IBr^-), when they are surrounded by different numbers of carbon dioxide (CO₂) solvent molecules.

To be the best they can be, optical atomic clocks need better clock lasers — lasers that remain phase coherent a hundred times longer than the very best conventional lasers. For instance, light from the clock laser in Fellow Jun Ye’s lab can travel around the Earth 10 times before it loses coherence. However, realizing the potential of the lab’s optical clock requires that the laser light remain coherent for 1000 trips around the Earth. The brute force solution to this problem would be to operate the clock laser at 4 K. This approach would increase the cost, complexity, and size of the optical clock as well as rendering it impractical for space exploration and travel.

Fellows Ana Maria Rey and Jun Ye have come up with a clever idea that should make it much easier to design a quantum computer based on alkaline-earth atoms such as strontium (Sr). In this work, they collaborated with former research associate Marty Boyd, former JILA Fellow Peter Zoller (University of Innsbruck), and colleagues from Harvard University and the University of Innsbruck.

The Greene group just figured out everything you theoretically might want to know about four fermions "crashing" into each other at low energies. Low energies in this context mean ultracold temperatures under conditions where large, floppy Feshbach molecules form. The group decided to investigate four fermions because this number makes up the smallest ultracold few-body system exhibiting behaviors characteristic of the transition between Bose-Einstein condensation and superfluidity. 

Imagine being able to study how molecules form on the quantum level. It turns out that researchers have already figured out some nifty techniques involving lasers and jets of reactive atoms for doing just that in a gaseous environment. Now graduate student Alex Zolot, former Visiting Fellow Paul Dagdikian of Johns Hopkins University, and Fellow David Nesbitt have taken this kind of study into a whole different arena: They recently probed the molecules that form when the surface of a liquid is bombarded with a very reactive gas.

Last year the Ye group conducted an actual laboratory astrophysics experiment. Graduate students Brian Sawyer, Ben Stuhl, and Mark Yeo, research associate Dajun Wang, and Fellow Jun Ye fired cold hydroxyl (OH) radicals into a linear decelerator equipped with an array of highly charged electrodes and slowed the OH molecules to a standstill. These molecules were then loaded into a permanent magnetic trap where they became the stationary target for collision studies. Next, Sawyer and his colleagues aimed supersonic beams of either helium (He) atoms or deuterium molecules (D2) at the OH molecules. They then studied the resulting low-energy collisions, which took place at temperatures of 80–300 K.

The "dark ages" of the early Universe drew to a close with the appearance of enough stars to strip electrons off most of the hydrogen atoms in the gas clouds between galaxies. By a billion years after the Big Bang, these reionized atoms had rendered the Universe transparent to light. About 12.7 billion years later, visiting JILA member Gayler Harford, Fellow Andrew Hamilton, and Nickolay Gnedin of the Kavli Institute for Cosmological Physics decided to investigate the structures formed by ordinary matter (baryons) and dark matter soon after the reionization process was complete.

An oxygen molecule (O₂) doesn't fall apart so easily — even when an X-ray knocks out one of its electrons and superexcites the molecule during a process called photoionization. In this process, the X-ray first removes an electron from deep inside the molecule, leaving a hole in O₂+. Then, an outer electron can fall into the hole, and a second outer electron gets ejected, carrying away any excess energy. The loss of the second electron is known as autoionization, or Auger decay.

In a rural northern Colorado landscape punctuated by plentiful corn fields, a tree farm, an abandoned feedlot, and a handful of McMansions, only one thing is certain: the exact time. The nation’s backup time scale, consisting of four atomic clocks, two measurement systems, and supporting hardware is tucked away inside radio station WWV's remote transmission station, located 12 miles northwest of Fort Collins. Fellow Judah Levine travels to the station site an average of once a week to check on the performance of the backup time scale, which he designed and built in 2005.

Researchers in the Kapteyn/Murnane group have decided to use soft X-ray bursts to watch the interplay of electronic and atomic motions inside a molecule. Such information determines how chemical bonds are formed or broken during chemical reactions.

Xibin Zhou and his colleagues in the Kapteyn/Murnane group have come up with a clever new way to study the structure of carbon dioxide (CO₂) and other molecules. The researchers use two innovative tools: (1) coherent electrons knocked out of the CO₂ molecules by a laser and (2) the X-rays produced by these electrons when they re-collide with the same molecules. The coherent electrons and X-rays are produced in a process known as high harmonic generation.

The mission to find the electron electric dipole moment (eEDM) recently took a menacing turn. Chief Eric Cornell and his protégés were already hard at work characterizing the hafnium fluoride ion (HfF⁺). Their goal was to be the first in the world to complete the mission. In their choice of molecule, they owed a lot to JILA theorists Ed Meyer and John Bohn (a.k.a. Agents 13 and 86), who had taken the theory world by storm in 2006 when they devised a simple and straightforward method for the evaluation of molecular candidates for an eEDM search.

Until recently, astronomers have had difficulty figuring out the composition and size of dust grains in galaxies beyond the Milky Way. They've had some luck with the Large and Small Magellanic Clouds (LMC and SMC, respectively). However, these two "satellite" galaxies are practically our next-door neighbors and much easier to observe.

Astrophysicists know that the centers of galaxies have supermassive black holes whose size correlates with the size of the galaxy surrounding them. They’ve also observed that galaxies collide and merge. In fact, galactic mergers were even more common billions of years ago in the Universe when today’s galaxies were still being assembled.

Fellow Konrad Lehnert needed a virtually noiseless amplifier to help with his experiments on nanoscale structures, so he invented one. Working with graduate student Manuel Castellanos-Beltran and NIST scientists Kent Irwin, Gene Hilton, and Leila Vale, he conceived a tunable device that operates in frequencies ranging from 4 to 8 GHz. This device has the lowest system noise ever measured for an amplifier. In fact, it produces 80 times less noise than the best commercial amplifier. More importantly, it adds no noise to a measurement system — a critical feature for a system probing the quantum limits of measurement.

The Jin and Ye groups recently crafted an entirely new form of matter — tens of thousands of ultracold polar molecules in their lowest energy state. The ground-state molecules are too cold to exist naturally anywhere in the Universe. But, like the Bose-Einstein condensates discovered in the mid-1990s, they promise to open the door to unprecedented explorations of the quantum world, including quantum information processing and exquisite precision measurement. That these molecules exist at all is a testament to the clever ideas and persistence of the Jin and Ye groups.